I'm still a Ruby fan but I share your immense, nearly immeasurable disappointment on the implementation of RBS. It's as though someone was tasked to add types to Ruby but do it specifically in a way that would guarantee zero adoption.

Out of curiosity, why was RBS so poorly executed and adopted?

They put them in separate designated .rbs files, so far out of the way that they might as well not be there at all.

You should look into rbs-inline. It's a huge DX improvement. The community spoke up and they are moving in the right direction now.