Is it just me or does this not seem as elevated and "good" as it should be for an item called "robes of the archmagi" as well as it being a legendary item. 

My chaotic good wizards' was royal blue and with a distinctly Elvish look

Make it look like what you want

There was originally something really long here discussing the relationship between humanity and morality, and though I tried to remain respectful it was questionable as to whether it was following the rules or not (Specifically the Prohibited Content stuff) so yeah I've removed it.

Its about the same as +2 studded leather

I’m about to have an armored class of 23 >:)

Yeaah, it truly is.  I play the UA 7 Warlock in a Descent into Avernus game (just leveled up to 10) and this  Robe just popped up on the random magic items store, and honestly.. I'm sooo tempted to lobby the PC's to buy it for me.  I.. probably won't.. because my character already stomps arse all around the yard in game, but Oooh boy is this tempting, and we have plenty of gold after selling the loot off a few high-value enemies.
I won't do it, cuzz I don't want to break the game, but the possibility of it will haunt me now.

I'm imagining an untouchable caster with this, bracers of defence and a ring of protection. It doesn't matter that they're not getting other casting buffs, AC will pretty much be be AT LEAST 20

Laughs in Bladesinger 

crazy

Yep... My player is a wizard Bladesinger and he's shamelessly breaking my game with this. He has an AC of 19, or 24 when he activates his Bladesong, and a spell save DC of 24. 😵

Where's the 2014 version ? it's not even linked to in the 2014 DMG. What is this ?

It is exactly the same AFAIK :)

I want one of these at level 14, my artificer can ignore all class, race and alignment requirements. 

Seems like they've just removed the alignment requirements. Maybe for the better, maybe not? Personally I liked to have my enemy wizards have these and not have to worry about my party's wizard getting one too early because of alignment mis-match!