Fan film by me. Any Karate Blackbelts on here? I trained in Wado Ryu Karate for two years an average of one, one hour class a week. I thought I saw some impressive skills but when I first got into MMA I was confused by the apparent absence of Karate guys. This perception for me changed with Lyoto Machida. He really showed that some of his foot sweeps etc. could be effective. He also showed that the deep stance could be effective if well practiced. I tried a deep stance at a couple of points in my Wado Ryu training and a couple of other TMA’s (although it wasn’t a commonly used stance just an option). I thought a stance like that would make it too difficult to move but Machida really showed that it could effective both for movement and against people trying to get under you taking you down.
"Karate" is too broad a term to confer much information imho. It's so varied. The Karate of Stephen Thompson (American point fighting) isn't the same kind of Karate as Machida (heavily modified JKA Shotokan from his dad) or even GSP (Kyokushin).
I think it really depends, you have got some Karate guys who are heavy into sport and some who are not. It's more of a perspective of competing, more than karate not being effective.