AKA Uncle Kano
It's not just f4. F2 is an insane normal that is ALSO 0 on block. It's a high, but seriously when the fuck are you neutral ducking Cassie when she has b2 that has almost the same range, and f2 leads to a KB if you try to mess up the stagger read, and leads to a mid with plus frames. It does have a bit of recovery, but the 1+3 part is not too fast either so it's not super obvious. Once you start respecting f4, she can get plus frames off s3 and that just gives her so much leverage since she's +3. And yeah 111 is super fucking good as an auto shimmy and can be made safe with glow kick which also has quite some pushback.It's a great move, probably one of her best, but you don't see players spamming it and winning matches because of it. It's a tool that's strong in neutral not one that beats neutral. F4 is good because of everything else she has. She might be the best character in the game if you put the effort in, but you do need a pulse to play her
Cassie is not this complex character, she's the simplest yet most effective footsie character in the entire game having acess to plus on block mids, super fast neutral on block mids, some of the best reach on hitconfirmable strings. Is safe on everything she does with hella pushback on her staggers thus having loads of neat little shimmy strats.
There's a reason why everybody is playing Cassie or has a pocket Cassie. It's not the Sonic effect, it's the 'damn this character super easy to pick up and be succesful with' effect. And yes she requires knowledge of fundamental footsies - thing is, her kit creates shimmy opportunities on block there for kinda setting it up for her without the player having to do much. You literally just f4, walk back as 7 frame jabs wont reach her and voila have your free combo. Such skill requirements must say. She takes no risks in her whiff baiting game - something everyone else except Kabal as to do. Kabal is at least punishable on his mixups and wakeups.