A lot of WP's architecture could be fixed internally, with shims added for backward compatibility. I took a stab at doing just that in a fork, but what I really don't know how to fix without major BC breakage is WP's reliance on global state. And these days there seems little point in incremental fixes, owing to the AI elephant in the room that doesn't need further mention. I suppose if WP were my livelihood, I might think otherwise, but even though I have several good friends in the WP community, I've pretty much written off the platform as a lost cause.