If anything, I find most of the levels too difficult. I’ve been stuck on 4337 for a couple of days, and it’s not even classified as a hard level. Every few levels I encounter one that can take days to finish. For me, that is flat-out boring.
I used to be able to complete 2 - 3 levels in an hour, but now I’m routinely stuck on 1 level for hours on end. King may call that more challenging, but I call that boring.
I agree @mcgirl, sometimes the hints aren’t the best move, and when I see an obvious better move I take it. But sometimes when the hint looks like a bad move, it ends up creating a surprising cascade.