Can't take him down if you can't close the distance. Dude has a comical 88" reach (Jon Jones is 84" for comparison's sake) and he knows how to use it with arguably the best jab in K1/MMA history. He's literally KO'd people with his jab
And if you were able to get him down, he actually has a decent guard. Nothing spectacular but not a fatal flaw either
I think people tend to dismiss him based on his Fedor fight (I've been guilty of this myself) but that's Fedor ffs
To put Semmy's MMA career into perspective: his first UFC fight was in 2001 and since then his only losses have been to the prime versions of Fedor, Nog, Barnett and Kharitonov