A long time ago i came to the same conclusion and suggested that a new feature/pvp event with certain restrictions would add a little more diversity to the pool of teams faced. It wouldn’t discard the possibility of some nerfs or adjustments to cards because sometimes some changes need to be made.
The devs “walked a few miles in this direction” to bring variety by adding positive incentives for using certain troops with the bonus from events and all. But to a certain extent it is not enough to provide real changes to the pool of “best troops to win” so i still think that having real restrictions controling the pool of cards could be more effective.