No. WordPress doesn't need 1,000s of block themes. Will it get 1,000s of block themes? There are more than 20,000 classic themes in the org SVN and I think actually we could see many times more variation in design from far fewer block themes than would ever have been possible with classic themes. In many respects working with block themes feels like going back in time and building theming from the ground up as it should have been, knowing what we know now.