My two cents: 3.7 rewards resilient players and handicaps efficient players. I myself made sure early to acquire level ten versions of every white unit for my own completionist reasons, as well as green units. Players that keep a lean line up will have to play catch up now.
ETA: if you think keeping low level white and green units is wasteful, you just don't know how to play in different ways. I frequently mix my level tens with level twenties and thirties to maintain raid/faction war minimum power requirements, if I used all my most powerful units every time, I would gas out early and lose the opportunity to keep raiding.