I think a restaurant in a touristy spot doesn't have to be good to succeed. They get plenty of foot traffic anyway, so they can be mediocre, or decent but expensive. They don't rely on repeat business. I found this to be true in Paris, though there are some good places in TS, but they are expensive.
We stayed a couple nights right on River Walk and I don't recall finding a place nearby that was notable. They can be decent, but I have better success "around the corner".