Remasters are usually outsourced to a company who does just that. Ports and remasters.
Or a small team (sometimes only like 1-5 people) work on the remaster)
The only gripe I get is them charging full price.
Other than that remasters DO NOT prevent development of new games. No company (except cheap ass capcom) is using resources that would otherwise be dedicated to new releases to make remasters.
Seems like the prevailing rhetoric is that the game industry is putting their resources into remasters instead of making new games. It's just not true.
Is it a cash grab? Yes. They can profit off minimal investment. Just like a blu Ray digitally remastered release.
Shameless? Maybe in some cases. But seems pretty simple to not buy them if you're not interested.