He hasn't been up to his standards in quite awhile, not since Pep has been at Bayern.
He's a great player at his best no doubt, but I said it in the transfer thread that it's pointless buying him when we have Alba. If you want a new LB to replace Digne, try going for younger profile player whose career wouldn't overlap with Alba's.
Alaba's entire strength is his link up play and overlap combinations with the winger on his side. His quality increases and decreases proportionally with the quality of what he's paired with there. He was the best LB in the world with prime Ribery, he was average with Costa, post-prime Ribery and one-trick-pony Coman, he's decent now with in-form Coman. It's a pretty simple formular.