It is possible to teach someone to throw 95 mph. However, it's only possible if that person is "capable" of throwing 95 mph. Unfortunately not many are "capable" of doing it and most who can, came by it fairly "naturally".
It's much easier to master "technique" while working on improving arm strength as much as possible. In many cases arm strength will never reach acceptable standards for certain levels.
If it were any other way professional catchers would be a dime a dozen, at least defensively.
That said, it is possible to improve both technique and arm strength. But the sad truth is... if God didn't give you a good enough arm, your chances of being a catcher at a real high level are very slim, even if you can throw it on the bag every time.
I understand that there are excellent catching coaches who claim other things are more important. I wouldn't call myself an excellent catching coach, but I agree with those who are... However IMO the other things are most important among the pool of candidates. To be in the pool of candidates you have to have acceptable arm strength.
Is the catcher with the strongest/best arm the best catcher? No, not for sure, because all the other things become more important. However, does anyone know of a Major League catcher with a weak arm?
To me, one of the prettiest things I can see on a baseball field is the catcher that has a true cannon! While all things can be improved, that is the most natural thing. When they convert a position player to a catcher, no one is thinking about the guy with a weak arm. Often it's the infielder with a strong arm or even a pitcher. Sometimes catchers even become pitchers because they have real good arms.