In just the first two episodes they have completely downplayed almost every major achievement/extraordinary act from Last Airbender. Toph single-handedly inventing metalbending and not even Aang ever being taught it in the show? From what I recall, metalbending relied on sensing the earth in metal, something only Toph could do because she was blind... but she also taught Aang that ability so he should have been able to metalbend. I'm sure that would have been useful... but now THE ENTIRE police force knows how to do it? This is the lesser of evils considering Toph founded the police force, but still... it makes metalbending seem way less awesome.

Then we have lightning. Less than a handful of people could do it in the Last Airbender... and they were ALL the most powerful firebenders. Ozai, Azula and Iroh were the only ones who could. Even Zuko couldn't bend lightning... but now any old firebender can bend it. From a triad leader to... a GROUP of people who are just lowly powerplant workers. WTF?

Then there's spiritbending(what Aang used to beat Ozai)... and even chiblockers are en massé now. Next all we need to see are a bunch of bloodbenders to come along and devalue all rare achievements in the old show.

Also it kind of bugs me that even after it war, it's still kind of pushing fire benders as villians. I mean sure you see some waterbender thugs but it seems like anything associated with important loss involved a firebender thug.

I wasn't aware of the lightning benders, but yeah I agree that makes those bending techniques less unique and cool.