The reality is that college players with serious NBA prospects have to play like that in their freshman and sophomore seasons. The top teams often start 4 or 5 underclassmen. When your roster is less talented, you point to youth and inexperience. While some solid NCAA programs do well in the tournament because they have some solid 4 year players, in college less "projects" than you think really develop over time - most NBA players step onto the college court exhibiting those talents. While beyond our backcourt there may be guys with potential to be good college players, at this point that's not enough to produce a winning season.
If you look around college hoops, really only Kentucky, Kansas, and Duke start all underclassmen and have much success. We can't expect to be them. The blueprint has and will continue to be Villanova, who always seem to have a good mix of upperclassmen and under.
Plus, it is easy to see why st johns fans place importance on experience and senior laden teams. We've made the tournament twice in the last decade and both of those tournament teams were essentially all seniors