I disagree. Tattichef is an anachronism, an entertainer from a bygone era who, like many others, is now having to compete with the advent of rock and roll. His chance encounter with the Scotsman, his gig in Iona and the attachment the girl has for him, genuinely believing he can produce magic and her subsequently leaving him when she finds love leaves the Illusionist disillusioned and he returns to his homeland.
It is a beautifully animated film with superb incidental music, composed by Chomet. You're right in that it isn't for everyone.