Exactly. The benefit to the Bootstrap boom was it elevated a lot of cookie cutter designs like a raft on a series of sensible defaults that were are close to sensible/good taste as some very talented designers could make industrial cookie cutter standards. Bootstrap enshrined smart, intelligent defaults like good color contrast and a baseline of accessibility for developers just copy and pasting and modifying what Bootstrap gave them. For a brief moment the "I just need to get this done" web had a good accessible baseline.

LLMs aren't starting from sensible defaults and don't have to meet WCAG scores unless you tell them to (and even then might hallucinate checks they didn't actually make).