Except every Chassidishe Rebbe ever. I don’t think it would be totally inaccurate to say the yeshivish world is also moving more towards being yichis-based.
That’s a gross exaggeration for chassidim, and an even grosser one for roshei yeshivos.
Not that yichus doesn’t have an impact, but there are plenty of cases where the son isn’t worthy and therefore doesn’t take over, and by roshei yeshivos, even where they do take over, that doesn’t mean they are considered a gadol. That has to be earned.