It depends on which /Article/ OP is eligible for citizenship under, under Croatian citizenship law. The law has also been updated by our parliament in the past year. I do not want to make any assumptions about OP's situation. When applying for Croatian citizenship, it is important to explicitly state in your "biography" (Životopis) which Article you are applying under, basically as your first statement.
Many people in the diaspora abroad are eligible under Article 11, which can be relatively straightforward but with some "gotcha" tricks, that the bureaucracy will deny your citizenship over. It is vaguely mentioned in Article 11 (in Croatian), that people who emigrated abroad--or people who are direct descendants of these individuals may become citizens, with X Y Z etc. conditions listed as requirements. One "gotcha" for example, is that you have to provide documented official evidence (from at least one government source--certified, Apostilled, and translated into Croatian) that your emigrant family member permanently emigrated from former Yugoslavia. This is not explicitly mentioned as a requirement anywhere in the law. But, implicitly, based on the documentation you would be providing for your citizenship application, you would think that a government servant could determine that your family member established a life permanently outside of former Yugoslavia. The only place where I have found official information about this requirement is on one single Ministry of the Interior webpage, which is in Croatian. (You do not have to speak Croatian at all to become a citizen if you are from the diaspora.)
If you are in the diaspora abroad and your family is from Bosnia, most likely you are not eligible under Article 11, and you are instead eligible under Article 16, which is way more difficult to obtain. Article 16 is way more subjective and arbitrary too, when it comes to requirements, so you can have a tremendously hard time with the bureaucracy.
The articles of the citizenship law (translated into English) appear dubiously straightforward: https://www.refworld.org/pdfid/5ac3799f4.pdf [Note: This is not updated with this year's amendments to the law]
It is a mistake to read Croatian laws exclusively via English translations, regardless of whether they are official translations or machine translated. You miss a lot of context and detail that is needed for success. Croatian is very concise, clean, and direct (with respect to interaction/communication), in comparison to English. The grammatical cases in Croatian contain a lot of context that is missed via human translation and machine translation into English, too.
All applicants must understand that every single Croatian government servant is "thinking in Croatian" when you are interacting with them (or your application), even though their English is fine and they are fluent. When I showed up at the Croatian consulate in Los Angeles, I was told by the consul general (who is now an ambassador in a strategic location in an EU country, to establish better economic ties) that I could not become a Croatian citizen, because the family members that were emigrants were my 4 great-grandparents (I am half Croatian and I am legitimately culturally American and Croatian through my family) from Dalmatia (coastline Croatia), rather than a grandparent or a parent.
I did not expect this "news" but I had come prepared. I showed him the "family tree" I created, in Croatian. Croatian citizenship law allows direct lineal descendants of emigrants, to the third degree, to become citizens. So, he counted the generations of my family, starting with me, and determined, right then and there, that I was right and that I could become a citizen.
The Croatian consulate in LA is the friendliest of all of them, and they actually have a handout now for applying. They also recommend providing a family tree in Croatian. Anyways, it is best to always call--not email consulates: They have to respond to phone calls. Some consulates are better than others.
Page 1: https://drive.google.com/file/d/1iL6ZPKgVj6XpWE8K7VlHocteW6G...
Page 2: https://drive.google.com/file/d/1WfhiDrg_VQRZOa6tmh-AxcucuBO...
Some people applying under Article 11 via their emigrant /parent/ have been granted citizenship within 1 month. See: https://vslavich.medium.com/how-to-obtain-croatian-citizensh...
I was granted citizenship off of my 4 great-grandparents (I only needed 1 to be eligible--but I provided full complete documentation for all 4 of them for the Croatian government) via Article 11 in 10 months. But, supposedly a lot more people are applying now during the pandemic, so now the wait is much longer.
If you make the simplest of mistakes; if you are not explicit about your requests; or if your documentation is not organized in a cohesive, easy-to-follow manner, then you are likely going to experience severe trouble. In that case, it can easily take 3-5 years, and you will need a lawyer to resolve your issues in court. One of the best things you can do is have everything, up to the most mundane details, set up to the point where the bureaucracy does not even get the chance to blink at your application. Since they are "thinking in Croatian", it is important to have spatial information in Croatian, such as diagrams and "family trees" if necessary.
Another "gotcha" is on the actual citizenship application form: The Croatian government asks you, in separate questions, "what are your citizenship(s)?", and "what are/is your nationalities?". Croatia, similar to Israel, is founded on the basis of (ethnic) nationality. In other words, your "nationality" is synonymous to your ethnicity. On the application, you are supposed to state "Hrvat" (masculine for Croatian) or "Hrvatica" (feminine for Croatian). They also ask for the "nationality" of your parents. For my mother, I put "Hrvatica", and she is 100% Croatian descent. For my father, it really is none of the Croatian government's business, and I refused to play that game, and I knew I could get away with it via the bureaucracy. I put down "American" as his ethnicity on the application, even though he is of northern European descent. At the consulate, they saw what I did, and they asked me what my father's true nationalities were, which I did answer truthfully verbally. It was kind of funny: It was an awkward situation for the other applicants and the consul general knew to smile and keep his mouth shut, like he had been trained to do.
While Croatians are friendly, some of the government bureaucracy via Croatian diplomatic missions in the US are not-so-friendly. Some people are assigned to the New York consulate due to residing in a state within their jurisdiction.
The New York consulate has tried many times to require that /all/ of your citizenship documentation be less than 6 months old, which is often nearly 100+ documents which includes pages that must be certified, apostilled (authenticated for international use), and translated into Croatian. Due to this strict timeline and ridiculous claim, you basically need to utilize Gantt charts to be successful at this hellbent endeavor. But, if you do your research, and learn some Croatian, you will find a webpage on the Ministry of the Interior's website, explicitly stating that only the criminal background check (in this case: FBI fingerprint background check) has be less than 6 months old for your citizenship application. I have helped many people with this issue.
Many people have emigrant family members who (illegally) transliterated their Croatian names when they arrived in America. A lot of people have last names that officially end with this -ić and their family member changed the ending to -ich upon arrival in America so people would pronounce their last names correctly. The correct way is supposed to be -ic in US English. Some people have family members with the name of "Josip" which the individual changed to "Yosip". Clearly, when the documents are reviewed (birth/marriage/etc. certificates), the name change is noticed and you can still tell that these documents are chained together and tie together the family genealogy which gives entitlement to citizenship under Article 11, for example.
The New York consulate sometimes tries to force people to make the name changes, in proper US English transliteration, on all of the documents. This can be an unbelievable gargantuan logistical task in the US, unlike some other countries. In some cases, it is impossible, because you have to get other family members to agree to change their name, as in their identity--and literally everything tied to it, which they have held all of their life, in order for you to get the documentation right, so you can get your citizenship.
Some people actually do this. But, when the New York consulate tries to pull this stunt off on people, I always recommend getting a Croatian lawyer to take over the battle, so that it is won.
Also, one of the modus operandi in Croatia is nepotism. Connections are crucial, and whom you know gets you places in life. So, one needs to be outgoing and just find people who will help out in situations like this.