Diamond and Pearl were the last games in Masuda's 3 game road map to revive pokemon after pokemania died at the end of gen 2. His plan was that there would be new games and then remakes to reintroduce the old pokemon, and that both of these would link to the ultimate experience.
Diamond and Pearl were the culmination of the whole series up until that point with the intent of being the best games. A barebones Let's Go remake would completely shit on their ultimate themeing and the series legacy.
If they are real then Masuda or whoever pitched it should be ahsamed.