When I first started learning Python / web frameworks, I went with Flask because it was smaller and "simpler". As my project grew however, I had to organize it. I was basically imitating what Django gives you by default, though less cleanly.
I have exactly the opposite experience: Flask is nicer than Django; SQLAlchemy is better than Django ORM. Love a bit of Flask.
Many of these independent components pale in comparison to their Django counterparts in glaring ways—they are often a pain to use, with some pretty questionable internal code choices. They remain used because they are often the only choice out there, even though their implementations are inferior to Django’s.
I say this as someone who has used Flask for over 5 years, as well as nearly 5 years of Django.
Parts that I mentioned are (or were when I compared) light years ahead (especially sqlalchemy).
I feel like most using Flask would consider “Flask components” to be equivalent to Flask extensions—e.g., Flask-SQLAlchemy vs SQLAlchemy proper. Maybe it’s a pedantic nitpick, but I’ve never heard anyone refer to SQLAlchemy as a Flask component in 5+ years, hence my comment about the distinction. But yes, many of the Flask-compatible Python packages you mentioned are quite a joy to use.
Some of the design decisions of Flask just don't seem logical, such as using the db instance when defining model parent classes. Makes for strange contortions when defining multiple model files to prevent circular references or db not found errors.
db = SQLAlchemy(app)
class User(db.Model):
...The obvious move at the time was to move to django and I spent some time familiarizing myself with it's own DSL. But boy was i struggling all along the way to do things how I liked in Flask with django. The Django Templates were extremely limiting (no modules) and couldn't even do regular python things and I came to find that extensions for Django were in no better shape than flask's. There was no clear solution for rate limiting and various other things I was looking for.
I've followed rails from a distance for a long time but, coming from python, ruby seemed so abstract to me i could just never figure it out but towards the end of my django time, i was finding that rails did/had everything i wanted and it all worked just the way i wanted it to and it was calling to me really hard. i took a big leap and spent a couple months diving fully into ruby, doing all the tutorials, reading all the books. at this point i am officially converted and my project app with it is already further along than i ever got with flask or django. when they say "ruby/rails is built for programmer happiness", they really mean it. and i can really feel/appreciate it. it's extremely fun to use and to see real progress without having to rack my brain and figure out some internals before i can proceed every so many hours. i'm just getting shit done and things work just how you'd intuitively think they should. rails ftw