Stick with Flask. I don't think it is a good reason to change. To be fair, you'll have the same maintenance issue with any language/framework. Some are better maintained, but I think Flask/Django/RoR are in the same league.

I'm a huge Flask user, with projects with 50+ Flask extensions installed. Most of them I just plugged in and never had issues. Some issues I had were easy to patch and most of them were fixed upstream.

You have some complex extensions, but a lot of them are just small wrappers, so it is possible it's just good enough and feature complete.