He'd fit in at pretty much any top team except for us and Chelsea.
We already know that he was brilliant/world class for Dortmund. We already know that he's brilliant for Japan. We already know that he was good under Fergie, despite struggling with injuries and adjusting himself to a new role. And according to Kagawa's former coach in Japan, Barcelona is the team that would fit him the best.
The crappy football we're currently playing does him no favors at all. Even Mata, who's been allowed to play in his favored position, is only a shadow of his own top level.
It's not rocket science. Crappy, slow, and static football makes classy players seem mediocre. Especially technical players who thrive under quick movement.
I agree with parts of what you say here, however Kagawa is slightly different to some other 'classy' players. I don't think every 'classy' player would look awful here, despite our non-exist system.
Silva, for example, would still do the business here in my opinion: The ball sticks to him more; he's harder to knock off the ball; he's more robust; and is much more comfortable holding the ball for a while with his head up, patiently waiting for the pass - aside from being technically superior.
I could imagine Silva coming here and raising our game, rather than being dragged down by it. He'd still be okay in a slow system.
Whereas Kagawa needs to release the ball very quickly otherwise he's liable to be knocked off it. And here, there's rarely anyone available for a first time pass, like at Dortmund.
I'd say Mata is half way between the two. And he's looked less lost than Kagawa, in my opinion.
I obviously agree that our play needs to be zippier. It comes down to centre midfielders. You can't build a quick, intricate passing game without midfielders who trust themselves and are trusted by others with the ball in tight spaces.
Carrick and the rest just don't trust themselves with anyone near them, so half the time they don't show unless they have space. But obviously you out-pass/unlock teams by going into the tight spaces they don't want you to enter, not the acres of free space they allow you.
A couple of centre midfielders, and though we won't be playing like Dortmund, we'll be zippier and more cohesive.
It's exciting, and I think he'll improve - though he'll never look as good anywhere else as he did at Dortmund, in my opinion.