You might wanna post this is either the Q/A thread, or the Video & Matchmaking one. That being said...
I'm no expert, but from what I see you are a bit impatient. Ganondorf requires you to play patient, especially against fast characters like Fox. Another thing is that you seem to use F-mash a lot. It isn't a move that you really want to use in neutral, only in read situations (like when you predict a Side-B from Fox).
Also, there are many times that you could have edge-guarded Fox offstage, which is important because of how slow and predictable his Up-B is. While you have the right idea about hitting Fox out of his Side-B, often it is better to use an F-Tilt instead of an F-Smash. It's faster and easier to do on reaction, and sends Fox at an angle he's guaranteed to be edge-guarded at anyways.
In neutral Ganondorf out-ranges Fox, so you want to make sure you are always in your optimal range. Also, Fox's blaster has about 30 frames of end lag, so if you see him using it, you may be able to catch him with a Side-B or Down-B. Fox's options from the air facing the opponent are rather lackluster, because he only has N-Air or F-Air, the second of which is somewhat ineffective. Don't be afraid to hold shield against Fox. He doesn't have any kill throws even past 200%, and none of his throws are combo starters (as long as you DI away after a D-Throw).
In conjunction with plethoric shielding, you seem to not know what is and what isn't safe on shield. None of Fox's grounded moves are safe on shield (with the possible exception of his Dash Attack), and his N-Air and D-Air is unsafe as well. Additionally, Fox's B-Air is vulnerable to perfect shielding, so if you're looking for something concrete to practice, you might wanna start there.
Anyways, take my opinion with a grain of salt; I'm no expert. Your own experience probably outweighs mine, so if something I say doesn't make sense, it probably doesn't.
