Bizz (and honestly probably all lesser ganons, so everyone except kage) doesn't know how to take ledge from a shino stalling sheik, so if he corners me I just stall until I can get past him for free.
You can crouch under his grab and his jab, so if you fair his shield then crouch in front of it you can usually reactively grab his whiffed shield grab (I assume all low level ganons spam shield grab).
Be really careful when punishing Ganon. 90% of hits I see ganons get are either from having center stage (which they get via respawn invulnerability) or from hitting people out of their own combos. Don't get hit out of your own combos.
Ganon is extremely simple. If he fairs, dash dance back -> fair him -> crouch will most likely get you a free grab. If his fair hits your shield, it's borderline impossible for him to punish roll away. You can threaten whenever you want - bait a bunch and don't go in predictably, because you always get to decide when to attack and on top of that all of his responses to your baits are highly committal and punishable (except jab, which doesn't even beat half the approaches you would fake, and if he spams jab you can run up -> crouch -> grab).
How are you losing neutral? Look at what you're getting hit by - it shouldn't be hard because Ganon uses about 3 moves. Don't go in the air, or he'll use his upair, which is actually broken lmao but it doesn't matter because your ground game ****s his ****