Should be an endgame reward in the form of "finishing" your covenant, earn enough renown from them that they will welcome you back anytime so you can venture to a different one. The soulbinds stay saved and activating them will also swap the two covenant abilities as well.
Even from a lore perspective, it makes little sense why covenant X is salty about me leaving after helping them immensely. It's not like they are some mortal enemies, they work together to fulfill different roles in the shadowlands.
Regardless some of the covenants certainly need a change or two. I was really digging the Necrolord Banner concept for warriors, reminds me of GW2 Warrior banners a bit but it's just soo garbage compared to the other 3 for any situation and spec.
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It will be sad to see Divine Toll going away, for me at least.