As you would expect it's a bell-shaped curve a few people with low ratings, a similar number with high ratings, and the rest of us somewhere in the middle. In Tactics Trainer there's a nice graph that shows the distribution of Tactics Trainer ratings for all the people who use it.

So I'm going to assume that is trying to set puzzles so that every member will find a puzzle that suits them at some point in the week. The latter is fairer to the greater number. It's probably in the nature of chess players to assume they know best, but let's for a moment assume that knows what it's doing better than every single one of its members. You can't keep all of the people happy all of the time you can only keep some of the people happy all of the time or all of the people happy some of the time. We all know (I think) that the easiest puzzles are on Sundays and they get harder through the week, with the toughest on Saturday.

Sunday today so at least half the comments about today's daily puzzle are about it being too easy.

Daily puzzle jigsaw