I started almost exactly where you were about 12 years ago. Came from a graphic design background, knew HTML and CSS really well, was decent at client side JS. I knew some PHP from hacking on Wordpress sites, but struggled to grok the rest of the web.
The best thing I did was grab a Rails book and study it, building the sample project all the way through. Then I came up with a web app I wanted for myself and built that using what I had learned. This took some time, but taught me so much. First, it forced me to learn another ecosystem, which made me much more aware of what was “common” or “universal” among web applications versus what was environment-specific. It also made me learn a new language, which similarly gave me a much better understanding of how computer programs work (seeing the same basic things implemented differently helped me understand the fundamental concepts that every language is abstracting over).
I would definitely still recommend this approach today, specifically because Rails is such a well-documented full-stack framework, it’s really easy to learn. Start here: https://www.railstutorial.org/
Another advantage is Rails is the tech underlying many of the web giants (GitHub, Shopify, AirBNB, etc), and the Ruby ecosystem inspired many of the other cool new technologies out there today. Even though it’s not the “hot new thing” anymore it’s extremely marketable. React devs are a dime a dozen, but people with Rails experience are in high demand and much harder to find.
The last thing is you just need to get a job at a place with other good engineers who can mentor you. Ultimately everything else is just getting your skills up enough to get in the door, once you clear that hurdle you’ll be able to learn as you go.
Best of luck on your journey, it’s hard work but very, very rewarding! Happy to answer questions if you have any :)