Legends Arceus was certainly an interesting game and I liked what it brought to the table, but my main point of contention is that all of that fun left Sinnoh with...nothing that will be remembered from its remakes besides the fact that it was the guinea pig for a new line that would get a massive upgrade in the region coming after it? ORAS will always be remembered for mega evolutions that turned Hoenn shitters into meta-defining threats as well as how the Nature Trio dominated the competitive scene after getting their upgrades, but PLA will be remembered for...introducing Pokemon where half of that cast originated elsewhere as well as giving two members of the Creation Trio throat cancer and an amputation (not to mention that those two kind of suck ass competitively)? There is obviously more lore introduced in PLA, but ORAS is not exactly lacking in that department either with things like the Delta Episode.You're reading a little too much into it I feel, I'm definitely not reading that much active malice in what Sinnoh got. And I'm saying this as someone who is both a Sinnoh fan and a Unova fan and grew up with both gens.
Sinnoh got plenty of love in the past two years. BDSP may be pretty ass but Legends: Arceus is really fun and a great and interesting way to revisit Sinnoh by being a Sinnoh "pre-make" and is by far the biggest risk they have ever took with mainline Pokemon, and we're talking a series that more often than not takes very minimal risks with its mainline games.
People forget Legends: Arceus was the real "Sinnoh remake" from Game Freak's POV and is actually indicative of a new direction they want to take old region revisits. BDSP was basically a "safety net" because PLA was by far the biggest risk they ever took, and while not perfect as it was using the flawed Sword and Shield engine it took off very well and is a great way to revisit an old region. It may not have been like HGSS and ORAS in every way, which in my eyes both peaked the "remake" concept in different ways, but it was a good way to revisit Sinnoh and was very deviant from classic mainline gameplay in fun ways. BDSP was basically the safety cushion they needed financially because PLA was both super different and was delayed two months due to COVID and couldn't make it to Holiday/Black Friday so BDSP covered both of those from a commercial standpoint as something that was guaranteed to sell while also incentivizing new players to buy PLA.
Teal Mask in SV also made some nice Sinnoh shoutouts with the Sinnoh starters being available as an egg from Jacq, and all three of them getting great buffs to make them better, Ursaluna getting a new form in the Bloodmoon form, and Perrin being Adaman's descendant and the PLA Wild theme being there as well.
Unova is getting a lot of love but I wouldn't say it's getting a "proper remake" as we don't know what's next after SV's DLC which is now fully out. Indigo Disk takes place in Unova in the future, and you have here an antithesis of what PLA did: PLA had ancestors of DPP characters, Unova has characters who are children/grandchildren of BW1/2 characters, like Lacey being implied to be Clay's daughter and Drayton being implied to be Drayden's grandson, and some BW theme remixes and whatnot and Meloetta, but it's definitely future Unova as opposed to PLA being ancient Sinnoh.
I do think Game Freak is done with doing by-the-number remakes with ORAS remaining the last of its kind. Which is to say, for all we know the next Unova game that comes out this generation could actually be another sequel to the BW series, since Black and White's follow up game was a sequel in Black 2 and White 2, the next game after SV DLC could be yet another sequel story in Black 3 and White 3 that follows up both BW1/2 and Indigo Disk, probably being concurrent with ID since ID is Unova in the future. That's very much something I could see happening.
Which is to say, we've reached a point in the Switch era where you never know what might happen.
I also understand that was Gamefreak's PoV regarding the remakes, but I find it difficult to believe that was not malicious - you are correct that we do not know what is in store for Unova right now, but the fact that it is getting so many shoutouts before the generation that its remakes are supposed to be released in is a pretty obvious sign that Gamefreak are approaching them with much more care than Sinnoh was given.
As for your points about the Unova remakes potentially being something a little different, I don't think they affect my argument - as long as it is in the format of a 'classic' Pokemon game and don't suck like BDSP, that is quite proper in my eyes for a remake.