As long as coaches are engraining good form over and over, there doesn't need to be the heavy contact on your own teammates in practice. It doesn't have to be only on bags either. There are plenty of drills that use your own teammates, but they are not done at full speed, nor do they require helmet or shoulder pads. We run these drills every day during defensive practice and it's solely designed to help progress the form while taking the head out.
A philosophical change our HC made about 5 years ago was to stop beating the **** out of our players with constant "full go" practice sessions and Oklahoma drills. The thought (and what we've seen as a result) is that reducing the amount of pounding in practice actually makes our kids healthier, fresher and more willing to get after it come game day.
IMO, the fundamentals must always be worked on, at every level, but it doesn't require constant beating all week to be physical and tackle well during games.