Again, an opinion, and not the correct one to me. Plenty of people play hog when he is not trash. In 6v6 the off-tanks get a role again and so we will need both rein and hog players. In fact, 6v6 makes it so we need all types of tank players, not just those queueing the tanks you list as the most popular (let’s hope nobody is queueing for Mauga though).
If you want to keep tank players in 6v6 then we need both main and off-tanks to be fun. Currently having tanks where the other team just picks Ana and they become useless is not fun at all (and rather stupid design - of Ana, not the tanks).