A user has to click a lot of buttons to make this work, android security is doing its job. If there's any failing on android security's part, it's consolidating permissions into accessibility services instead of breaking them out into something a user might get scared to click.
Then again, they did click accessibility services on a "secure messaging" app. They need to learn somehow. I just refuse to accept that the appropriate solution is not owning things you buy. There has to be a better way.