first of all: i don't hate legendairy's, i don't hate legendairy users, and i don't hate legendairy haters.
and now my little argument why legendairys are not lazy:
first: legendairys are harder to catch
second: getting a legendairy with good IV and nature is even harder than catching one
third: training a legendairy is harder. asuming, YES JUST ASUMING!!! that you take 1 day to train a zigzagoon from lvl 70 to 71, then it would take a week to do the same with a legendairy poke. AND I AM NOT SAYING THAT IT REALY TAKE'S A DAY/WEEK!!! :D
fourth: legendairys are not unbeatable. any pokemon can be beaten by a good and welltrained pokemon with a type advantage. as far as i know there is only 1 pokemon type that has no weakness, and that is dark/ghost. and there is no legend with that type combi.
that is why i think legends are not lazy: they are harder to train, harder to catch, it is harder to get a good one, and you still have to think before you use it.