The fact of the matter is that 99% of true D1 kids will get noticed and will have an opportunity, if their grades are in order and they have kept their nose clean. The people who say that they didn't go D1 because their HC didn't do enough for them are full of crap. Now, if the HC blackballed them and intentionally told potential recruiters that the kid was a bad egg, then that is a completely different conversation.
Every single high school in the nation with a football team is being recruited by some level of college coach. College coaching is a very tight circle and people talk. For example, if you have a D3 coach recruiting a school and he sees a kid that he thinks is a scholarship type of a player, he will generally know someone at the D2 level who can offer that scholarship and give the other coach a heads up. Conversely, D2 coaches identify kids and pass them along to 1-AA coaches and so forth. One of the main reasons that information is passed along so frequently is because coaches are always looking to move up. D3 coaches want to become D2 and D2 wants to be 1-AA, etc. Now, I am not saying that good players always end up at the exact division that their talents are capable of, but for the most part, each kid is appropriately recruited. In this day and age, if a kid has the talent and desire to play college football, they will be afforded that opportunity.