e2e encryption is a net loss for a lot of use cases. Particularly, most DMs are spam in my experience.
Spam prevention is much harder if the server can't see the message. Spam reporting can be done with sufficient effort, but stopping the known spam from reaching the user in the first place is impossible (the closest you can get is a client-side scan before actually showing the message to the user, which requires downloading the whole message just to show "number of incoming messages" indicator or else having the indicator lie).
And of course, E2EE is a lie if you're visiting a website anyway.
It is my understanding that many E2EE chat systems won't actually E2EE your initial message to someone you aren't already mutual in-app contacts with.
Either E2EE is something you "upgrade" an existing conversation into (only after both sides consent to the conversation); or E2EE is something that only inherently establishes once both sides have sent one-another a message; or E2EE is something you can only enable before you start a conversation, if you already have the other person's public key (which you only get when you request to add them as a contact, and they accept.)
I think schemes like this balance privacy with spam-prevention quite well: privacy-conscious people can explicitly add each-other before either person says anything / can send intentional small-talk as pairing messages; while everyone else gets the benefit of a central spam-filter sitting between them and messages from strangers.
Spam prevention is much harder if the server can't see the message. Spam reporting can be done with sufficient effort, but stopping the known spam from reaching the user in the first place is impossible (the closest you can get is a client-side scan before actually showing the message to the user, which requires downloading the whole message just to show "number of incoming messages" indicator or else having the indicator lie).
And of course, E2EE is a lie if you're visiting a website anyway.