The fa, fifa & uefa can moan all they fucking want about flares, but they're fucking boss for the atmosphere & make clips & photos like that look well better.
Imagine any mental European away & you always picture smoke & flares.
No pyro, no party.
What I would say though is that it's a bit worrying that clubs can't stop people taking in large flares like that though, if they are actually making an effort to, simply because you can make pipebombs etc of very similar size so makes it apparent that stadiums are still an easy & valid terrorist target.