Certainly there are helicopter parents out there who have ruined their millennial children. Of course, this has always been the case to some extent, particularly among the wealthy. I personally know a man in his late 40s who calls his parents when a light bulb in his house has burnt out and needs changed. He's not developmentally disabled or anything, he's just been that sheltered for his whole life. His parents are getting on in years, and some of us seriously worry how he'll even be able to feed himself after they get too old to take care of him.
My experience, teaching ~120 undergrads per year for the past few years, is that I've had perhaps one student per year whose mom tried to contact me to interfere somehow with his coursework. I've spoken with colleagues about it, and they find it happening at similar rates. I haven't looked at any studies about it, but it doesn't seem to be the biggest problem.
I think what's much worse is that freshmen are coming into college woefully underprepared. It seems like they spend too much time in high school doing standardized tests and not enough time actually learning how to write and do mathematics. I teach courses to sophomores that require solving simple equations for unknowns and working with ratios, and some of those kids are quite intimidated by it. IIRC, it must be something like middle school-level math? Maybe high school freshman? And some of them can barely construct an intelligible sentence.
Nevertheless, most of my students work hard and get the job done. Some number fail every year, but my score distributions come out looking pretty normal at the end of every semester, so that's something, at least.