For apps I've built in the past, I've found the hardest thing was having to pay monthly hosting costs for years (which is pretty much a necessity if you use a cloud SQL database that things like Rails and Django rely on heavily).

Even $10 a month becomes annoying after 5 years.

I built this: https://forever-free-cloud-app-starter.chriszhu.me/ as a way to build a basic CRUD app that would be free to host forever.