The "faithful" remake stuff is just there to cut corners and save time. Why bother trying to reimagine a modern Sinnoh region when you can just copypastE the exact same map and say it was done "to be true to the originals" or something? Oh, it's lacking all of Platinum's improvements? That's because its being FAITHFUL to Diamond and Pearl, silly!
What's worse is that the "faithful" stuff only applies to things that are easy to do, for example, it was too much trouble to code in all the contest move types and effects, which is why BDSP cut the performance part of contests and just made the whole thing one big minigame. It'd be a pain in the ass to make actual collectable for Underground, so now you just get retextured models, ect ect. Everything is "faithful" until they get to the hard stuff, then suddenly its totally fine to go into a new (AKA easier) direction.
It's so much easier to just adapt a game from 2D to 3D than it would be to take something resembling a risk and do things like redesign and revamp places and characters to match modern Pokemon. Think about how cool a properly fleshed out Veilstone City would be or a more interactive Orebough Mine would be, now think about how that would take actual effort/talent and you understand why they went with a sad remaster.
ICLA is an actual nothing studio that just does grunt work for GF/TCPI, they likely have no actual artists or designers on hand for anything past UI which is why everyone in BDSP looks so fucking ugly, and GF wanted it like this because they didn't want to run the risk of hiring a REAL studio and getting outdone at their own game while they continue to fart out ugly ass games like PLA.
tl;dr BDSP is intentionally bad, GF is using ILCA as a scapegoat by giving them a game they can't handle so they have no competition when it comes to making Pokemon games.
