This is dumb logic. Split player base concern is not for protecting the popular game modes, but for protecting the other game modes to keep their populations high enough to warrant using.
This is several years ago, but Jeff Kaplan gave us a day’s snapshot one time of stats for various game modes by region and platform.
For EU for that day, 99.8% of all hours played were in just 9 game modes. Splitting the player base is a very real concern for the borderline fun, but not extremely popular modes.
There is a very good reason Blizzard has limited how many options players can pick from to keep people finding Qs for even the lesser played game modes for the given period of time and chunk of the world you are in.
Its why we have lost various game modes that weren’t popular enough or had them in rotations too.