>>23344888>>23344899FR/LG were pretty necessary with RSE only having like half the Pokédex, and they at least offered a lot of new content.
HG/SS weren't entirely necessary but made getting a lot of Pokémon much more convenient and are probably the single most polished games in the series despite Gen IV's HM cancer and engine problems.
ORAS were not necessary but could have and should have been much better than they were.
I've always thought it would be a much better idea to revisit old regions with new games rather than remake old ones directly, but that requires levels of effort that don't let you spend less than a year on a game that sells 10 million units in a month
