[mikeash]

Your statements could be totally reasonable. Difficulty in a game can be good or bad, it all depends on why and how it's difficult. If that tough level is hard because it's well designed as an interesting challenge and you can get past it with practice and thought and it remains interesting while you do that, it's good design. If that tough level is hard because it's unpredictable and requires excessive luck to get past and forces you to go through lots of tedious replays when you fail, it's bad design.

I have no idea which category this falls into, just pointing out that your examples can be legitimate.