Headcanon that the Fuzzlies first language isn’t English which is why so many of them speak broken English.
Those who mainly stayed away from humans for whatever reason, either due to being scared or because they just lived in an area where there weren’t as much humans didn’t bother learning it in depth. Sure they could pick up basic words and with context clues, figured out what even more meant, however that’s as much as they picked up on.
Certain Fuzzlies though [ Terry, Harriet and Squeaky Peepers ] were in close proximity with humans mostly, either because they were privileged enough or were surrounded by humans who loved fuzzlies were taught more English than the rest.
Of course the more they spend time with humans, they’re gonna get more better with their English, just not right now