They are NEVER open! And when they are, it's not what you'd call an open stadium anyway. Sunlight comes in like a beam, making it tough to see.
I still say that Pittsburgh has my favorite relatively modern stadium. So Fi....The Dallas Palace...Atlanta's Mercedes Dome...... They are fancy looking but sterile as hell and I have zero desire to see them. See the Rams play in them? SURE! But modern stadiums just don't excite me at all.