When I was on the team I believe the largest complaint was the lack of individualism in planning and there seemed to be little realization that all athletes cannot be coached the same. I can't speak for the cross country, MD, or Distance guys, but for the short sprinters and jumpers I rarely recall workouts being tailored for the individual. E.G. If jumper X has a problem hitting the board in the long jump, but has a great take off and landing it seems confusing that he was would be doing the exact same things in practice as Jumper Y, while jumper Y's problems are the exact opposite of jumper X. In short, everyone cannot be trained the exact same way and receive the same results.
Now i'll attempt to address the walk-on issue as i saw it when i was on the team. I believe people felt they did not receive the personal attention (coaching-wise), that they thought would by joining a College-level program, because the coaches were stretched thin by the number of walk-ons.
If we look at the issue as objectively as possible, I'm sure we could all agree there is a mix between short-comings of athletes and coaches from the earlier posted list. Some people posting negative things are doing some because they are upset and others are posting positive statements because they see a few big names and assume that means everything is paradise, while probably a larger number were just thankful they had the chance to be on a DI team. I would suspect there is another large number of people, who for a various number of reasons, always assume that when athletes leave the team, regardless of whether they quit or were kicked off, should be treated as weak, disrespectful, or just brats. As i hinted at earlier, this fits for some, but this does not accurately cover the entire scope of individuals.
I had a medical withdrawal after hip surgery. I had spoken with the coaching staff, the academic advisors, and everyone else who needed to know about my decision, but learned over the summer that I was no longer welcome on the team come next fall. Just to be clear, i'm not using this to bad mouth the staff, but just as a real life example to say that everyone who isn't on the team wasn't so because they could not perform or could not handle the workouts. Beyond that, you can infer what you'd like from the post.