There's a level where you're constantly under attack. There's a level where you lose your creature, which is the game's main perk. And there's a level where it's impossible to progress without using brutal and extremely tedious means. And there's only 5 levels, so that's most of the game for you.
It's like somebody said "Hey, we got the fun stuff out of the way, now let's have every kind of annoying mission a game can have, one after another".
I thought the game's first three lands were great, though you're right that the first area is arguably the best. I can see what they were going for with land 4, and it could have been very rewarding, but I never felt the catharsis by breaking the curses that was probably intended.
I did not like land 5, though.