Having a similar code base size for a mobile app, I believe you. No noticable issues with its size.

> You think that after my 500h of work and daily usage of my own app, I have no idea about what maintenance looks like.

At 30 users you have no idea what maintenance looks like. That's literally what maintenance is - responding to real world usage.

Come back with your experience when you have lots of users that stick with your app, you're putting out fires and implementing new features. Your experience will be meaningful after 6 months to a year.

I'll wager that right now you have a PoC that needs a lot of work to be something that retains users. That's not a criticism, that's just how it works for every startup.

I have been QA testing, fixing bugs, and adding new features near full-time for the last seven months.

I have a pretty good idea about what maintenance looks like. Particularly so about the technical aspects of how effective the models are at refactoring or fixing bugs.

Even if I were to accept the argument that users would have entirely different expectations for my app than I do, it hardly changes the fact that I already know I can easily implement large changes in the code base.