I've used Flask/SQLAlchemy and Django a bunch in my day, professionally and on the side.
It's a different strokes for different folks sort of deal.
Django is very opinionated, in a way that is "eventually" correct (i.e. they might have had some bad opinions many years ago, but they have generally drifted in a better direction). If the opinions don't align with what you're building, the escape hatches are not generally well-documented or without penalty.
Flask is minimalist and flexible. Once you find a "groove" to building with it that fits your sensibilities, it's quite, quite nice. That being said, the most recent versions of flask have excellent documentation, imo, and the tutorial is a bit more opinionated in a highly productive way. The "patterns" section of the docs is also super useful for productionizing your app.
Personally, I prefer the combo of Flask+SQLAlchemy, and eventually Alembic once you decide that's good for your app's maturity level. I respect Django a lot, I just enjoy the explicitly "less magical" aspects of a Flask stack, which is an opinion-based trade-off imo.
As a minor rebuttal, I get sick of Flask because it is bring-your-own everything. Nothing I write will ever NeedToScale(TM) or be off the beaten path from the Django Way. No interest in plugging in an alternative template language, form validation, email library etc. When I get stuck in Django, I know someone else has experienced the exact same situation. With Flask, I have to pray to deity that Miguel Grinberg has written about a similar enough situation. The majority of documentation foregoes Flask Blueprints.
It's a different strokes for different folks sort of deal.
Django is very opinionated, in a way that is "eventually" correct (i.e. they might have had some bad opinions many years ago, but they have generally drifted in a better direction). If the opinions don't align with what you're building, the escape hatches are not generally well-documented or without penalty.
Flask is minimalist and flexible. Once you find a "groove" to building with it that fits your sensibilities, it's quite, quite nice. That being said, the most recent versions of flask have excellent documentation, imo, and the tutorial is a bit more opinionated in a highly productive way. The "patterns" section of the docs is also super useful for productionizing your app.
Personally, I prefer the combo of Flask+SQLAlchemy, and eventually Alembic once you decide that's good for your app's maturity level. I respect Django a lot, I just enjoy the explicitly "less magical" aspects of a Flask stack, which is an opinion-based trade-off imo.