what they really need to do is improve Boomerang itself. Moving Boomerang to HBO Max isn't going to solve anything. The way I figure it, it isn't going to solve the problem of:
not distinguishing between half-hour episodes and individual segments
-stalling; among other things, they have yet to add any of Hanna-Barbera's* other shows (moreover, their Paddington Bear series was taken down some time back)
If anything, if Boomerang were to be discontinued, and everything on it added to HBO Max, it could actually make the problem worse. Plus, I don't think some people will like the idea of paying $15 every month just to get the stuff they want to see. I mean, if you were only interested in Boomerang, would any of you actually pay that much just for that (and maybe the Cartoon Network originals), while avoiding everything else? Oh, and please don't give me the "came for [x] stayed for [y]" explanation. It's the principle of it. Don't give me the "you can log in with your cable/satellite/etc. provider" explanation, either. In the first place, it won't be widely available for while. Second, that's not the point, either way. For some people, it's a lot to ask for just to watch the stuff you want, and ignoring anything you don't.
The bottom line is, Boomerang needs to remain a separate service, and also needs to start improving. Otherwise, it will really just start causing more problems. To put it another way, "be careful what you wish for, you might get it".