1) Despite an appearance of being "left leaning" (according to polls of faculty political sentiment) they continue to gatekeep education behind prohibitively expensive tuition that is out of reach of lower economic strata without crippling debt, and have simultaneously struggled to produce graduates whose economic differential easily makes up for that expense and lost work time.
2) They enjoy a tax free status while receiving significant tax money despite many failing to grow their student bodies in tandem with the growth of the US population, leading to people questioning whether they deserve those benefits as institutions that serve the public.
3) There is a sentiment that basic literacy and numeracy of graduates has dropped over the last decades outside of a narrow area of studies, because of a shift to a model where students are customers buying a credential instead of getting an education.
(These are all interrelated, of course.)