E2E is only a thing if you trust the app at both ends - which in a lot of E2E solutions means a closed-source blob that could be collecting and sending back the exact same data but mined from the client. It's not a panacea unfortunately.
Can't really openly sell it the same way if you are supposed to be E2E ..
And it's not like open-source is a panacea either, for most people who will not build it themselves you usually can't really know what is deployed/distributed.
Was going to use Element as an example but on F-droid the app is built and signed by the platform and an archive with sources is distributed.
But last I check the same can't be said for the play store and you have no idea what's running on app.element.io and there is an open issue for reproducible build for the electron app.
But at each step you are gaining something it's not "only a thing ...".
I fucking hate apple but the model they're taking is to take reasonable steps to frustrate state level actors (minus the CP photo upload thing) and as such have set a standard that needs to be followed.
Apple has done a wonderful job marketing something that doesn’t Turkey exist.