This is just a problem of lack of familiarity with the space. Crab apples are indeed much less palatable than Red Delicious apples.
Although its ability never to oxidize and turn brown feels downright unnatural. You can leave a cut cosmic crisp on the counter for days and it just stays yellowy white. Weird.
However, I find cripp's pink to be wildly variable. Some are beautifully crisp and very tart, these are my favorite. One store by me sells them and they just taste like red delicious, despite having the color and whatnot.
The sourness of Cosmic Crisp is probably why it doesn't oxidize readily.
I buy honeycrisp only for its texture, so I can't comment on the sweetness ratings as it's not my thing.