They already can worship together. Any catholic is welcome to come into any catholic church and to fully participate. It is the bizarre and highly legalistic RCC that needs secret commissions to get approval for backdoor treaties, and to have them scrutinized by legions of celibate male legal scholars etc...to see if they can worship together.
Ummm, my denomination practices “closed communion” and I think (perhaps hope) many others do as well.
“Celibate male...”
You’re slipping. You left out “wearing dresses.” Oh. And you forgot “altar-boy-raping...”