Oh god, please. Yes! I am sick of all the same looking pages, all streamlined. Does anybody remember the classical frameset from the 2000s? Left Navi frame, top frame, main frame. So boring. Everybody had it. It's the same today.
There is a benefit to UI uniformity for "boring" stuff like business sites and backends: less cognitive overhead or learning curve. When I see a standard issue wordpress bootstrap site I already know how to find stuff.