Why would they not block? Gen Fu is crushing highs 24/7, and mids quite often. He's faster than almost everyone to boot, and he can pop-out CH you at almost any moment with his crazy about of delays. Fighting Gen Fu is kinda playing a perpetual lose-lose scenario where you have to perfectly guess correctly the entire match, when you have about a 10% chance of doing so.
Free Step Dodge
Brute
Force_of_Nature
Because grab spam is against the Scrub Code.