I'm going to say exactly the same thing that helped me in this position. Be patient. Power shielding is your best friend but you can also mix it up with jumping, spot dodging, and rolling around projectiles. Ganon is somewhat hard to actually get off stage if you plan ahead (ex.some people have already mentioned trying to stay on the inside of the stage, but another one regardless of where you are is shielding and making them think they can get a grab, or jumping towards them and jumping back so they come at you). The psychological decision behind a lot of projectile users is to bombard the opponent with projectiles until you get close, or until they see an easy attack, and then use one sweeping move to knock us back, where we would need to start our journey up the stage all over again. Focus on that one piece; make it their weakness. Bait that one attack out of them, and if that's not enough, bait another one. For example Link loves his Fmash and Dsmash in this position. Samus loves her Fair. If you can get near them, they will have to do something; run away or fight. You NEED to understand what Ganon AND the opponent can do in every situation, and decide whether or not it's worth making the attack, or if you can make them do something. Ganon shouldn't really make an attack unless he knows it will hit. Sometimes I'll take a hit just to put myself in a position favourable to me, but only if I know the attack that he will probably use WILL put me into a good position. In conclusion, Ganondorf is all about capitalizing on your opponents mistakes and playing defensive, but if you look at it in an offensive mindset, you can out think the opponent and they will always be doing things you want them to do. They know you are slow, they WANT to abuse that.