One of the key features that distinguished Pokèmon Let’s Go from its predecessors was the fact that random battles were removed. In their place was a system where Pokèmon spawned randomly within the world and the player could choose which to encounter and which to ignore. Today’s presentation of Pokèmon Sword and Shield showed off just a small sliver of gameplay, but that was enough to indicate that this system has been removed in favor of classic random battles.
Right at 1:25 in the Nintendo Direct you can see the player walking slowly into the tall grass before randomly encountering a Pikachu. This runs counter to what Let’s Go had, which would have had various creatures spawning around and in the grass, letting the player either walk up to them to try to capture or run around them. Returning to random battles could spark some controversy among players, as the Let’s Go system was highly praised by many longtime fans.
There always was going to be distinct differences between Let’s Go and these Gen 8 titles. However, many hoped that Game Freak would retain the evolutions to the series that fans enjoyed. However, just keep in mind that we are currently in the dark in a lot of ways and all of this is based on short clips from an already short presentation. Wait until more info is officially confirmed before getting too upset or excited either way.