I did Flask and I thought it was so much work to do a login system and other stuff.
There were so many ways of structuring your codes. I find myself constantly rewriting the code to adapt to a new way of organizing codes.
I personally prefer a somewhat opinionated framework.
But I understand that there is a pro and con and a need for a barebone/slim framework versus a featureful framework.
I actually moved from flask & vuejs 2 from last year to phoenix & jquery.