The changes made upon LBP1 were pretty massive, in such a way that absolutely every element in the game got a revamp right down to the basics. If you look at the finer details in the new create mode you'd see that it would have been a pretty momentous task to change all of it through mere updates.
The dislike for LBP2 is probably due to all the gimmicky levels. I only started playing LBP2 very recently because we're finally starting to see some decent levels that aren't just silly retro-clones of things. If you still own the game keep an eye out because some of the levels that are starting to pop up are absolutely amazing.
Oh and yeah LBP2's story mode sucks

It's mostly just as showcase for new things ~