If you treat it like real mail it ends up exactly the way the OP describes: a few high-value messages at risk of being lost in a deluge of low-value, often unsolicited, noise. My real mail is so full of stuff I don’t want and don’t care about that it makes me resistant to looking at it at all - in fact, the only reason I do (and irresponsibly infrequently at that) is because of mail that occasionally arrives that has legal or financial implications.

I think it’s reasonable to expect that sender-controlled messaging ends up in this state, particularly when the messaging platform is incentivized to support this model.

ETA: typo fixes