They disrupted the integrity of the series. Personally, I wasn't ready for the fact that you could level up a Paladin to level 40 and single-handedly defeat hordes of black dragons.
And I think that many of you have repeatedly created many hero-less units and then got very tangled up in them.
Add to this the lack of upgrades (THIS IS AN OUTRAGE) and a poor castle development system...
although despite this, I still play them... A paradox, however.