There is a difference between "running the opposition as though it wants to win" and "setting out to beat the players," at least, I think, in attitude. I would describe the latter as "adversarial," but not the former.Perhaps it comes down to how strictly one defines “adversarial”, but I think a DM can take an adversarial approach and still be a fan of the player characters. The DM, at least in 5e, is not really trying to “win” every combat after all. They are trying to present varied challenges that, like you are saying, make for a game experience that is fun for the table. At the end of the day, if proper expectations are set up front, then concerns about an “adversarial” DM can be minimized.