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.

Better how? What science? Do you have a citation? Most comparative diet studies are only observational with multiple confounding factors and no proper controls.

E.g.

https://www.nhs.uk/live-well/eat-well/red-meat-and-the-risk-...

and

https://progressreport.cancer.gov/prevention/red_meat

I’m not going to single out studies and pretend that I’m in any way into this field.

The wikipedia page states more correctly: "animal meat, other than fish".

Fish have lots of selenium that meat lacks.

Fish can also have lots of mercury that meat lacks. It's probably best to eat a variety of different foods in order to avoid excess toxins and nutrient deficiencies.

There’s some interesting research suggesting that mercury poisoning is in fact just pulling out the availability of selenium for bio chemistry by forming metal ion complexes

https://pubmed.ncbi.nlm.nih.gov/18761370/