Bug in tactic trainer ?

I begin to notice, that more often i see problems with a very low passing rate, still beeing adressed as simple problems, i not realy understand it. It seams to me that problems with a low pass rate must be very complex. Because the number of problems you get is limited for a bronze and free memberships.
I'd like to see problems matched to people's level. As otherwise if those kind of problems keep cumming up and are not matched then well people never climb up. Climbing up itself is not realy an issue, but people like to learn from problems that make sense to them

I began to ask myself why did i became bronze memeber ?
To practice more, but if we get puzles that are not near our level then it doesnt make sence to practice chess-tactics here. (makes me consider if i should use different chess sites), no i'm sure this site rocks, and so i prefer this site, maybe someone can take a look to it.

below a sample of such a problem, there are more of them

Incorrect move - good try!
You got 4 of 7 moves (57%) correct.