I don't know that I'd agree with the notion that games that are engaging need to be rated higher. Is there harm to playing one game a lot?
I've read books that were so engaging I kept reading long after I should have stopped for the night. The author very much intended for the book to be engaging and to hold my attention. Should we rate the book as more mature because I kept reading it?

I don't think balatro is any more addictive than most other games, it just has a low barrier to starting and a quick turn around.

Ratings should be informative and harm based. "This game is full of violence" and "this game has gambling". Factual.
A game being prone to being played alot isn't factual, it's just an observation that some people find it fun. Without an associated risk of harm you're just putting a scary number on something because of your opinion about it.