According to science it should be better than red meat. Additionally, a lot of seafood comes in smaller portions, is full of bones, shells and whatnot, whereas it’s relatively easy and cheap to get large quantities of fully edible red meat. It’s not that you couldn’t have a pound of peeled shrimps, but my own experience with seafood says it’s not very common.

So overall you’re most likely ending up eating less meat, and not just different meat.