I think most altoholics are pretty okay with something between “getting to max level” and “delve gear is enough” which pretty much eliminates the need to worry too much about keeping up on the chores and not falling behind the curve to keep getting invited to content etc.
You don’t want alts, you want more mains, which as you found out isn’t sustainable beyond a certain point for most people.
Not much you can do tbh.
If you don’t play enough to at least maintain the M+ Vault Row on multiple characters (without hating yourself), you won’t keep your “alts” caught up and they’ll feel weak vs your actual main and therefore less fun in content.
Kinda just how it is.