This is a rant about dumb password policies enforced by some websites or apps. If you see these password rules forced to you, try to stay away if possible.
Can't use special characters, or use a pre-defined special characters only
Are you storing the password in plaintext that your database will break when have special characters?
Password can't be longer than X characters
Most probably storing the password in plaintext and their database column is limited to those characters limit.
Password expire every X months, without notice, suddenly can't login. Reset it and can't use the last 5 passwords
They store your previous passwords, either encrypted or plaintext.
If you already an expert in python, you can keep doing that and build a frontend in python using Dash. They have bootstrap components and mantine (React) components for options of style you might prefer. Don't need to write JS or HTML. It's enterprise grade and widely used by large enterprise projects.
Another is Reflex but their open source version is tricky to run in production. They promote more of their cloud version or enterprise license.