“For instance, I often had to rely on the web browser to access services like Reddit, Telegram, and Discord since native apps weren't available. Web apps work for primary use but can't always replace dedicated apps, especially for banking or fitness tracking.”
That’s the core of the problem these days. Nowadays, there’s so much that requires an app to work.
Avoiding mobile apps was entirely realistic in the 2010s, but it’s too late for that now. The world has changed, that ship has sailed etc.
If you can isolate yourself from certain realities of the outside worlds, using a fully FOSS system can be done. The technology is there. It’s just that most people can’t isolate themselves to that degree.