If you are using a device managed by Apple/Google/Microsoft, E2E is merely a roadbump - it means that your device owner needs to push a backdoored update to it, rather than simply reading your data server-side at their leisure.
Which is still valuable, to be clear: it's a pretty large roadbump. Either you're such an important target that they're shipping a specific update to you alone (in which case, frankly, you didn't stand a chance), or they risk exposure.
But if you install a little snitch that reads your messages and reports you if they match some complicated, necessarily hashed pattern, then that roadbump is mostly gone. All the guy in Cupertino now needs to do is update the patterns to match what they want them to match, without anyone noticing.