Ya that's a good point for competitive scrabble. However today I think a lot of people's main exposure to Scrabble comes from WordsWithFriends (and recently, the new NYT games version). In those games, there's no penalty for getting a wrong word, it just won't let you play it. In that context, I at least think it would be nice to have a setting with a more limited list... it could be like Chess timed variants.
It's obviously an impossible challenge to draw those contours in language. Wordle did pretty well though! And going the other direction, just allowing everything that could possibly a word, just starts getting ridiculous.