You have a valid point. But I've seen people criticising remakes (not Pokémon remakes) for offering little aside from shiny graphics. Star Fox 64 3D, namely, because the only new thing the game brought aside from better graphics were the gyro controls nobody used because they're so complicated.
I mean, if you want to play through the game again, why not just get yourself VBA and a rom and play with that. Better yet, use an emulator for a mobile platform. Graphics shouldn't be THAT much of a concern.
On the other hand, the GBA games were the last ones to come with battery-powered saves, and these run out after a while, so anyone who plays a GBA Pokémon game won't experience the full features of the game (the saves remain but no clock-based events occur), so you can't plant berries for example.
I'm waiting to see what GF comes up with regarding these remakes, since they always add something. I didn't like the additions to Kanto in FRLG, however, since they felt tacked on in retrospect. Contrary to that, I welcomed the changes to Johto and new Kanto in HGSS because they turned the games into what they should've been if they didn't have constraints back in 1999.
I didn't want these remakes because I didn't think how they could advance the series further but, now that we have them, let's see what's in store for us. Which is why, if I get them, I won't get them on release date.
I think the biggest appeal is that we're going to play through Hoenn with the updated mechanics of 6th gen, but usually GF wastes that potential by not updating the trainers' rosters, so I'm expecting to fight Glacia's two Glalies and Sealeos again. :P
If anything, it opens the door for further remakes, even though I don't think it's necessary to remake Sinnoh (and I loved Sinnoh) and Unova.