Game Freak had to remake Pokémon models for Sword/Shield - Pokémon Sword/ Shield - Gamereactor

An interview from last month resurfaced after continued concerns about the new game, extending beyond the Pokédex alone.

Game Freak Artist Says 3D Pokemon Models Were Reused For Sword And Shield – NintendoSoup

Pokemon Sword and Shield Model Remake is Not the Problem to Me