top humans have been improving too; i'd estimate that quackle is stronger than most human players today, but the very best (especially nigel richards! https://fivethirtyeight.com/features/what-makes-nigel-richar...) can hold their own against it. i'd like to see the top-level-human win rate drop below 25% before i'd call us decisively outmatched, and below 10% before it hits the "don't even expect to win a game unless you're an expert" stage.
also, there's an (afaik) unexplored area of scrabble AI where you take into account the fact that some plays are harder to spot than others, and some words less likely to be in your scrabble vocabulary, so if you're playing a weaker opponent you can play risky moves that might cost you against an expert but will win big against a weaker player. unlike in go, this really matters because tournament scrabble uses spread as a tiebreaker; learning how to not just win but win big against weaker players is an important skill in some tournaments.
also, there's an (afaik) unexplored area of scrabble AI where you take into account the fact that some plays are harder to spot than others, and some words less likely to be in your scrabble vocabulary, so if you're playing a weaker opponent you can play risky moves that might cost you against an expert but will win big against a weaker player. unlike in go, this really matters because tournament scrabble uses spread as a tiebreaker; learning how to not just win but win big against weaker players is an important skill in some tournaments.