Bring Back National Dex - The resoning behing cutting features comes from Gamefreak's "desire to surprise players with new gameplay" (Ohmori, 2019).

If you really think about it this is a roundabout way of saying "We're taking stuff out so we can add something we removed back in later and get praise for it"
also like the rubbish example of the bike, and not something more substantial like oh I don't know, the battle frontier?

HG/SS tried to add nearly every major element Pokemon had up until that point by mixing Gen 2 with elements introduced in Diamond/Pearl/Platinum. They are considered one of the best games in the franchise.

Yet they really didn't do much new. Outside of a few superficial minigames like Pokeletheon, the Pedometer, and new ideas to old mechanics like Safari Zone, it didn't do much to 'surprise' the player. It simply brought a solid experience.

I'll admit that if this was all Pokemon ever did, it would get old even faster than it already does, but there are times when removing content is appropriate and times it's not. No one talks about the bike being removed in Gen 7 because you could ride a Tauros instead. Everyone almost embraced the removal of the Roller Skates because of the wonky controls it brought to exterior locations that couldn't even be changed.