I'm sure end-to-end encryption is great and all, but if a company like Facebook is giving you the client, what difference does e2e encryption make if you're try

I'm sure end-to-end encryption is great and all, but if a company like Facebook is giving you the client, what difference does e2e encryption make if you're trying to prevent Facebook from seeing your stuff? Obviously you can see the plain text messages even if it was encrypted, and so Facebook/WhatsApp could theoretically see it too. Isn't this true of any app, e2ee or not? Adding ads at that point is just trivial - process on the client.