I have a gut feeling that SerenityOS is going to have the same kind of progress that Linux had. Started as a little hobby side project "but nothing serious" but could eventually become something that ends up being a really useful. We will see where it is in another 5 years. Coming from a completely fresh base means that it has not gather the same technical legacy as others and that could really play to its hands in years to come.

I don't like how it's written in C++ (and I'm not a Rust person either)

And you hate Python as well, so, which language is your cup of tea?