You're extrapolating from an exception.

EGCS was created because Cygnus, a company whose business was based on GCC, wasn't getting their patches to GCC, maintained by non-company FSF.

Cygnus outcompeted FSF by so much that FSF folded and made EGCS maintainers new maintainers of GCC.

I just don't see average open source project being forked and improved by so much that it eliminates the original.

This requires 3 rare things to happen:

- the project is important enough

- the project is half-dead

- someone is willing to out-compete the original project

That won't happen to e.g. Laydbird. Yes, it's important but it's making rapid progress and they also use ai, so you can't outcompete them just using ai. It's a full-time project for at least one person (Andreas Kling) so unless you manage to find a band of great, unemployed programmers I don't see how you would compete.