Trying to control aggro in 5e, to somehow "tank" and absorb hits for the rest of the party, is definitely a fool's errand. (If you want to absorb damage for the party, play a twilight cleric.)
Being extremely hard to hit and damage is not useless, though. Survivability is its own form of utility.
Exactly. "Tanking" in 4e actually meant controlling enemy attention, because controlling enemy attention was a thing you could meaningfully
do, and the mechanics made it both worthwhile and necessary.
In 5e, it just means being extremely survivable. And if your features have intimidated the GM into
ignoring your character, congratulations, you've just
proven that your technique is overpowered for the narrow thing you've chosen to specialize in, and now you can take advantage of this unwise decision on your GM's part.
The core problem with Bladesinger is that doing wizard stuff is game-altering, whereas being a melee warrior is pretty straightforward.
But, if you want to be a melee warrior, Bladesinger is right at the top of powerful, versatile options.
Precisely.
Though I must admit, it's
really funny to hear Zardnaar assuring us that being a good Wizard makes you strictly better, stronger, more powerful than trying to be a highly-defensive combatant. Because he's spent quite a long time insisting to me, personally, that the Wizard is actually one of the
weakest spellcasters in 5e, while Fighters are (supposedly) really really really strong all on their own.
Like...if a Wizard can personally elect to just
strictly outclass the Fighter at one of the core things Fighters
do, namely, being really well-defended.....and
everything else the Wizard can do is strictly stronger than that...it seems like a pretty unavoidable conclusion that the Wizard class is, simply, better than the Fighter.