Personally I think supporting SMS is what's "out of touch". It's a legacy system that a huge chunk of their users won't have ever used in the app except possibly accidentally.
This will allow me to use my Apple iPad charger or my Apple MacBook charger to charge my Apple iPhone. Not being able to do that currently is not innovative, it's annoying.
Basically no-one does all of that in one app, so using Signal for Signal messages is normal for those people.