Pokémon has long had the tradition of having an enhanced third version releasing after the main pair of games for a generation. While much can be said about how the practice had a lot of downsides and it's good that they've fully transitioned to the DLC approach (so long as the base game is given enough development resources that it doesn't need fixing), past third versions are an important part of Pokémon's legacy, even being effectively the canon versions some of the generations. However, when it comes time to remake old Pokémon games, third versions are increasingly being ignored.
At first they were doing a pretty decent job at including things with the only significant missing things in FRLG and HGSS being the encounter tables, Cerulean Cave layouts, and arguably the anime stuff from Yellow (it can be debated if Yellow is a true "third version" or not, since Blue filled that role in Japan), but starting from ORAS barely anything from Emerald was included at all. You had some allusions to Emerald content, like the Deoxys animation referencing Birth Island (which wasn't even properly Emerald content but wasn't in Ruby and Sapphire originally) or the infamous "Battle Frontier Project has started" sign, but the actual content was completely absent. Even some Emerald adjacent content that was already in Ruby and Sapphire got completely gutted, like the Sky Pillar. I realize that the story of Gen 3 would make it difficult to incorporate everything into Ruby and Sapphire, but surely there was a reasonable solution somewhere out there, even if it involved remaking all 3 games.
Unfortunately, we seem to be going through this again with BDSP. There seems to be some incidental Platinum content included, and the added Pokémon seem to be present (albeit only in the Underground), but otherwise the game seems to be very aggressively ignoring Platinum based on the trailers so far. Even incredibly minor things like the improved regions aesthetics or the back button on the Pokétch are missing. They haven't even shown the Platinum outfits for Lucas and Dawn as a customization option, which is just a completely baffling omission. Perhaps we'll get some minor post-game Giratina thing, but Delta Episode is not encouraging. Ideally I would have liked the remakes to use Platinum as a base, something which would have been able to work perfectly fine if they handled the box legendaries like Sword and Shield did, but even a separate Platinum remake would be preferable to just completely ignoring it.
It's just very frustrating that the remakes are so incomplete, and it seems like we're just going to have to keep putting up with this. I'm entirely expecting Black and White to get remade without the sequels, Sun and Moon to get remade without USUM (which honestly might be for the best, there were some pretty controversial changes in USUM), and Sword and Shield to get remade without the expansion pass when their turn arrives, because they just seem completely determined to not include any sort of post release additions to these games when they remake them.
At first they were doing a pretty decent job at including things with the only significant missing things in FRLG and HGSS being the encounter tables, Cerulean Cave layouts, and arguably the anime stuff from Yellow (it can be debated if Yellow is a true "third version" or not, since Blue filled that role in Japan), but starting from ORAS barely anything from Emerald was included at all. You had some allusions to Emerald content, like the Deoxys animation referencing Birth Island (which wasn't even properly Emerald content but wasn't in Ruby and Sapphire originally) or the infamous "Battle Frontier Project has started" sign, but the actual content was completely absent. Even some Emerald adjacent content that was already in Ruby and Sapphire got completely gutted, like the Sky Pillar. I realize that the story of Gen 3 would make it difficult to incorporate everything into Ruby and Sapphire, but surely there was a reasonable solution somewhere out there, even if it involved remaking all 3 games.
Unfortunately, we seem to be going through this again with BDSP. There seems to be some incidental Platinum content included, and the added Pokémon seem to be present (albeit only in the Underground), but otherwise the game seems to be very aggressively ignoring Platinum based on the trailers so far. Even incredibly minor things like the improved regions aesthetics or the back button on the Pokétch are missing. They haven't even shown the Platinum outfits for Lucas and Dawn as a customization option, which is just a completely baffling omission. Perhaps we'll get some minor post-game Giratina thing, but Delta Episode is not encouraging. Ideally I would have liked the remakes to use Platinum as a base, something which would have been able to work perfectly fine if they handled the box legendaries like Sword and Shield did, but even a separate Platinum remake would be preferable to just completely ignoring it.
It's just very frustrating that the remakes are so incomplete, and it seems like we're just going to have to keep putting up with this. I'm entirely expecting Black and White to get remade without the sequels, Sun and Moon to get remade without USUM (which honestly might be for the best, there were some pretty controversial changes in USUM), and Sword and Shield to get remade without the expansion pass when their turn arrives, because they just seem completely determined to not include any sort of post release additions to these games when they remake them.