I think in the long term, such a project could be more sustainable than projects focused on an “original” experience.

KDE, GNOME, etc spend a lot of resources on new features and overhauls to enable new features. A fixed-feature replica project by comparison would eventually achieve a “finished” state, with resources instead going towards optimizations, bug fixes, code correctness, etc which are overall less demanding and make unavoidable tech migrations (e.g. X11 → Wayland) less of a pain since the project won’t be mired in tech debt.