Sure it's more limited in scope and use compared to Fealty & Statecraft which have widely useful bonuses, but I'm not sure that's a bad thing. Authority also limits you to a very specific playstyle: you're going to lose if you aren't constantly fighting. I'd even argue it's more limiting than Artistry.
I'm not saying we shouldn't touch artistry, but I don't think it's as limited in scope as you think it is. Even if it is more limiting compared to the other medieval trees, I'm also not sure that's necessarily a bad thing. To me, it has its clear use, and it's powerful but not broken. Having its drawbacks is probably a good thing too, otherwise civs it synergizes well with would get overpowered.