It is a legitimate gripe that remakes don't address or fix some problems of the originals even if other titles did. It's like Gamefreak is trying to keep the spirit of the original games for all the wrong reasons.
Emerald did have more than just Battle Frontier, it also had gym leader rematches for one, something that Gamefreak really goes back and forth on including. I also really didn't like what ORAS did to the game corner. While I know they couldn't keep it, what they did instead just seemed spiteful (like they didn't need the passive aggressive message, they could have just removed the booth entirely if they didn't want to replace it with a mini-game or something). ORAS had a really weird Berry Master's Garden too, in this donut layout that wasn't as productive as X/Y or R/S/E's berry gardens. The TM expansion was great, but TM's on the mirage islands weren't that great (even if luckily most weren't that good. I'd riot if ice beam was stuck in those RNG islands).
I'm indifferent about the Contests, as they did make them more accessible but at the same time super easy, unlike before when they were kind of challenging and really inaccessible. But I'll give props for Gamefreak for trying.
I'm not doing to deny that ORAS is better as a whole product and did add a lot onto the original games. They made Magma and Aqua actually cool villains instead of the worst teams in the series, and Sea Mauville was an interesting experiment in interactive storytelling. But I'm also recognizing that some things were lost in the shift, even if they were minor.