Mirth I don't know. I don't pretend to be an expert on non-Arsenal players.
However I've seen Kepa make some ridiculous mistakes in the past, which has formed an image of his quality. Couple that with the fact that he failed remarkably at Chelsea and you can see why I'm not a fan of this signing.
Could well be that he became a brilliant keeper at Bournemouth and would objectively be a good signing for us, but I'm still skeptical. I'd be a lot happier were it not for the fact that he's ex-Chelsea.
Players fail, signings don't pan out the way we always hope they would. But if you sign someone that had previously been a laughing stock at your rival and he inevitably fails again, it makes it 10x worse.