When my son started HS, we were so happy because we thought that finally there would be coaches who weren't dads, who were committed to helping all the boys become better players. And, we found that to be correct, although we did not quite expect that the players would be still doing instruction and workouts on their own time in addition to team stuff.
So I assumed that college would be one step more professional than that. That the coaches would be hired because they knew baseball and were good at teaching it and would have every incentive to do so for all players. D3, of course, is very different from D1 in terms of practice time allowed with coaches, and we knew that, too. I think it has worked for my son, he has gotten help when needed, and he works and studies baseball very hard on his own, too.
Also, as a non-baseball person, I did not realize how many different parts there were to pitching - not just mechanics, but also scouting opponents, pitch sequencing, analytics, etc. I am continually being educated about something new. I say this for readers who might not be experienced in pitching. No coach could handle all of this with an entire large staff, and no doubt some PCs are better at some parts of it than others. I'm going to assume that college PCs are looking at more than just velo and mechanics when deciding how much and what kind of effort to put into each pitcher.
Having said all that, there has been much conversation recently about changes to recruiting rules, and the fact that college coaches won't have as many years to talk to recruits. I do wonder, what was said in all those years of conversations? Did it lead HS recruits to believe that the PC would develop them and help them improve? Are those who are disappointed mainly late recruits who did not spend years talking to the PC?