Most restaurants IMO don't know how to cook fish. They over grill it, fry it and generally the fish is dry. So they cover the fish with lots of sauce and that is what you taste not the fish. OTOH some fish like Dorado ( Mahi Mahi) and halibut really have any pronounced flavor so they need something on top to flavor the fish. The best restaurant I know for fish simply salt and pepper the fish add a touch of olive oil and grill it slowly over mesquite. When its almost cooked through-but still not completely they serve it on a plate with a cup of melted butter for dipping-that's it. By the time your plate arrives the fish is done but not dry.

Personally I like old school. Salt and pepper the fish, bread crumbs, butter, back to bread crumbs then into a well seasoned hot frying pan for brief minute or two each side and serve with lemon butter.

And yes, fish that is frozen as close to the catch as possible, is better than fish "claimed" to be fresh that sit in a market until they no longer legally can claim its "fresh". (roughly about 14 days)