lol, I can only assume you're kidding OP. Bladesinger gives up School abilities sure, ... but is also a full arcane caster with mega AC.
My being underwhelmed has nothing to do with the power level of the sub-class. I acknowledge in the OP that that's fine.
My being underwhelmed is more to the fact that it's essentially pure wizard with a tiny splash of fighter - and that the "optimal" way to play the sub-class is to just stick to being a wizard with very little actual fighter/mage stuff. It's just IMO - which is why I asked if I was missing something.
I will say that the people who have played the 5e bladesinger seem to really love it (as evidenced by this thread and a livestream or 2 I've checked out)- so obviously it's got something going for it!