There are certainly issues with psychiatric disease diagnosis, but I also don't think it's surprising MDD diagnoses are high (the real number in that age bracket seems to be somewhere in the range of 10-20%). AFAIK the DSM criteria for MDD only require a single depressive episode.
Having a depressive episode at some point over the course of a lifetime should be seen as normal IMO. Someone can have a depressive episode and benefit from help at the time just as someone can develop a bacterial infection and require treatment. It does not need to be thought of as a chronic state, even though in a minority of cases that will occur (and is obviously much more debilitating).
Sometimes medication is extremely beneficial, other times it is not, but very few people are just being pumped with/kept on meds. You can see here that only ~6% of people with a diagnosed depressive episode in 2017 were treated with meds alone: https://www.nimh.nih.gov/health/statistics/major-depression
Of course most therapy is going to include work on lifestyle habits like what you've mentioned. While many of the people regularly receiving therapy were also on a medication, it is standard of care to do meds + CBT as they have well-documented and independent impacts on depression recovery.
It is normal to taper off use of antidepressant after a first depressive episode, and I think it's safe to say most people doing combination treatment will have proper oversight of their medication use. Maintenance medication is mainly suggested for those with a history of recurring episodes.
I'll also note I don't think this has anything to do with money grabbing. Prozac remains the most prescribed antidepressant, yet it is not under patent. Therapy on the other hand can cost an arm and a leg. Of course therapy cannot be mass-produced, but from an individual prescriber perspective therapy is more likely to be financially incentivized.
No doubt psychiatry is still operating largely in the dark ages, but that's simply because it is a hard problem (and perhaps some institutional incompetence mixed in). Drug development for psychiatric disease has actually mostly hit a wall, and numerous pharma companies have cut neuroscience research departments, because these clinical trials had a low enough success rate that the R&D costs could no longer be justified.
Further, I agree that lifestyle decisions can have a bigger impact than people think, but this sort of anti-medication attitude and thinly-veiled accusations of laziness only push patients away from good lifestyle changes. Depression can make it harder to do those things you mentioned, and it becomes a very nasty cycle. Medication can help break that cycle if used properly.
It is indeed important to make clear that the meds are a tool and not a magic cure all, and I hate the common sarcastic remarks that get posted in depression groups like "thanks exercise cured me". But I get where some of that defensiveness is coming from. Let's all try to acknowledge that a treatment plan is going to involve multiple pieces, different pieces for different people, and is not going to be easy or perfectly effective.
There's a fine line between helping and enabling, but a lot of people seem to err so far on one side that they either applaud terrible behavior or talk down to people about symptoms that they don't fully understand. Meds can be a lifesaver for some and are not desirable for others, that is something that needs to be determined by the patient and their care team(s).