That's the sorta standard socially accepted way of thinking about this. but uh... to a lot of people it doesn't ring quite true.
For example: if your life objectively sucks, why aren't you doing anything about it? Some people whose lives suck fix their lives, and other people get depressed and do nothing; what's the difference? And: all of us know somebody who appears to have a good life and therefore their depression is presumably a chemical imbalance thing but if you're being honest the vibes in their life are a bit off, actually, like you can tell they're not really getting everything they need out of it, that they're clearly good at masking (for example people who are clearly not thriving in their relationships) .... in which case sure medication could help but you can't shake the feeling that facing the reality of their life would help a lot more.
However! Questioning this stuff becomes a bit of a moral minefield. "Believing" in the chemical imbalance theory is part of why it's medically helpful. If your life has sucked for years and you could find no way of fixing it and then SSRIs helped, then you basically need to believe that it really was a chemical imbalance, because believing that it might not be threatens to take away the thing that's making your life work. So much so that I would bet at this point there are already readers of this comment who are ready to angrily reply to my preceding paragraphs, because the model I just described threatens their existence. (If so, wait a sec and read the rest...)
On the flip side, for some people not believing in the chemical imbalance model for some particular case might be important. Maybe they want to feel responsible for their life being bad, so they will be motivated to do something about it, and being happy due to drugs would make them feel complacent and okay with years passing by at a shitty job or something. Or picture someone whose parent has gone their whole life unable to take them seriously as an adult, which as a result means the child and parent have a bad relationship, and then picture the parent complaining about depression and taking medication for it. This can be really infuriating: the child thinks about the parent, "your life sucks because of the tension created by not treating people around you with respect, and you're so incapable of recognizing this even when it's told to your face regularly that you're taking drugs to feel better despite not fixing the problem". Now ascribing depression to medical problems seems like avoidance, and having people write off your frustrations and say that you're just depressed and need to take a drug for it is frustrating.
Just saying: the two narratives really get tangled up. I don't really know what to do about it, but I do think that some harm is done by harping on the concept of a "chemical imbalance". A lot of the issue is avoided if you just think of the drugs as helpful but don't choose any model (with its moral implications) for what exactly it is they're helping with. Just treat them as a tool for making you feel better.
Also, I suspect that people who have an intuitive aversion to mental health drugs are probably way overindexing on that intuition. I definitely did this for a long time, as did some friends I knew growing up. Turns out whatever your issues you can sometimes just deal with them sooner than later if you accept that doctors might be onto something. (Actually I think the reason people get stuck avoiding medication for so long is precisely that they feel like they're not allowed to be skeptical of them... which makes them kinda plant their feet in the ground and refuse to be open to it. That's kinda why I'm typing this long comment, to tell anyone reading that it is a reasonable thing to feel. And now that you know that maybe try them anyway..?)