College baseball does exist, but it's not a de-facto minor professional league like college basketball and football are. Even the lowest level of the professional minor league system is stronger than college baseball, and it's perfectly normal for strong enough players to be drafted directly from high school into the professional minors.
And since NCAA is a cartel, they can't sell their labor on the free market without moving abroad...
Of course, the quality of undergraduates has some effect on morale among the researchers - one imagines that the professor and graduate students teaching a course colloquially called "Stars for Stoners" must be wholehearted evangelists and/or be dying inside a bit every year. But this is largely isolated from the research itself, and you'll always find diamonds in the rough - undergraduates who are truly passionate and capable at a graduate level. They do great work.
If anything, the parent post may be referring to students who come from "feeder schools" which provide tremendous amounts of preparation and everything-on-the-legal-side-of-this-entire-controversy. And though those students are slightly more likely to be immature when they first matriculate, they too end up finding their passions and work ethics, and making great contributions of their own. Sure, the very same resources that let them enter those feeder schools tend to help them when they graduate. But if anything, it's good that the university can now count them as alumni, and that they can help their fellow graduates with networking and continuity of the collegiate experience. Research universities are a well-balanced system, and though there are many reforms that can be done, the systems as a whole work well.
Both groups think the system "works quite well".
Ivy admissions criteria make a lot more sense if you realize that they're engineering the makeup of the anointed upper-crust of the next generation (which only the most naive idealist would think is tightly related to merit). Tech is an unusually meritocratic industry (for now), which is why, at least in my experience, the brand power of the educational institutions on your resume aren't that great a predictor of success in the industry.
I get that it sounds like my sample is skewed heavily towards tech,but I can only think of one or two people out of my high school friends/acquaintances who went into tech, so this particular sample isn't skewed that way