If I were a Barca fan I'd possibly cut him a bit of slack. It's his 1st half of football in the CL ever. In this circumstance it's more about a reaction to your own mistakes than actually having made them when you've never before prepared a team for a CL tie. Zidane bombed @ Wolfsburg too.
As long as he learns from this and makes some ballsy moves, he's OK.
His mistake is trying to bring back a dead style. This style was only really successful with 3 or 4 GOAT players like Xavi, Iniesta, Messi, Alves playing at the same time in their absolute primes.
This is like LVG's United now and expectedly so. Take out Messi's individual actions and it's literally the same level of play.
Setien is like a random fan of prime Barca who is stuck up in the old times. But the fans wanted this and pretended that we're playing amazing while grinding against Granada at home so it's all well deserved really.