I felt the exact opposite and it's the reason I stopped playing sun, once I learned it didn't have the full national dex. The journey up to the champion fight should be majority new mons, but post game should absolutely open up to the full dex

Don't watch it if you don't want to? The og anime has terrible pacing and is incredibly intimidating to new fans. A remake can both find the packing and allow new fans to get into the series without stressing about catching up to 1100 episodes. Everything you think is special about the original anime will still be there able to be watched whenever you please, the remake is not taking anything away from you