Okay, I'll push back on each of these.
1. Well, yes, this is true. However, this was the case with the Artificer, which was released, so, there's that... Furthermore, thanks to bounded accuracy, "dead level" design that is consistent, and the restriction on bonus actions per turn, WotC has made balancing multiclass options much easier on themselves.
2. As was the case with the Artificer making Conjuration Wizards no longer the sole source of class-specific magical objects. This isn't an argument.
3. Using this hypothetical, if one rotating DM likes Divine Magic, and the other doesn't, you could run into the same problem. Or, if one DM likes monstrous races, and another doesn't. Also, it does not establish Psionics as having the same cultural prominence as magic. This is kind of rubbish, in my opinion.
4. Okay, I'll grant you that.
5. Yep, but this varies by table. For example, at my table, people who don't even own XGtE play XGtE subclasses, because we share our books with each other.
6. Where was this said?
7. What you want matters no more than what I want. This is what I like to call the Narcissus Fallacy, believing that just because you want or don't want something, you're right. It's just a personal bias (which you're entitled to), but it doesn't mean anything.