We can use Street Fighter expressions, but that doesn't mean we're talking about Street Fighter. Heavy characters in Smash, historically, have never performed well against faster characters. At the end of the day, good frame data and safe pressure define the meta.
The only real counter-example is Jiggs, who does all right in Melee solely because she can instantly erase someone's stock. And even then, only 1 person is really making that character work. Getting close to Ganon safely and getting back out again is one thing--that's what characters are supposed to do. The problem is that getting close to Ganon unsafely isn't nearly as threatening as it needs to be.
Historically, heavy characters in Smash without projectiles have just been booty buttcheeks period, so something's wrong with the designer's choices to begin with. It's not useful to think of this as "Well heavy characters traditionally suffer against rushdown in smash, so that's how it should be in the future".
It's more useful to look at it the same way as SaltyKracka. Ganondorf struggles against characters keeping him away with projectiles. He also struggles against high mobility characters getting all up in his face since he doesn't have strong options to deal with them once they're there. He also struggles against characters with disjointed hitboxes at midrange. When you struggle at every range, you have a character that has not been designed as well as he should have been.
Generally in other fighting games, the heavy grappler character has the disadvantage of having difficulty getting close to the opponent, but with the payoff of when they do, the opponent has a very difficult time getting away and they risk taking a lot of damage when they try. This means they need to have fast, powerful options at close ranges, so they generally should do well against rushdown characters. Rushdown characters have good mobility and can get in easily, which is their advantage, but they should always be worried about some kind of big punishment if they decide to get up close and personal against a grappler.
The Street Fighter comparison is Zangief/Yun/Dhalsim as Grappler/Rushdown/Keep Away style of plays respectively. Yun can beat Dhalsim because Yun can approach easily with divekicks even through Dhalsim's fireballs and long stretchy limbs. Dhalsim also has a tough time getting away from Yun's rushdown.
However Yun doesn't do as well against Zangief because even though Yun can get in easily and does well at close range, Zangief is better. At close range, Zangief has his very, very fast (this is key) and very powerful Spinning Pile Driver grab and easy to use anti air lariat if you try to avoid the grab. Low health Yun now has to think really hard and carefully about when he should get close to Zangief or risk ending up as a stain on the ground.
So unfortunately, the situation we have here is Ganondorf who struggles against characters keeping him away, and faster characters get up in his face just laugh as they dodge his sluggish attempts to punish them for getting close, and instead punish him.
He needs a fast option up close, I feel that even a fast jab is the least they can do because it's just a jab, it's not even going to KO anybody, just get them off. Or make his grab not a garbage piece of crap with no range and poor follow up options compared to other characters. Or bring back thunderstorming, something that only more skilled players will even know about, and only benefits him once he's already done the work to get close.
Considering how god awful Ganon was in Brawl and how he continues to under-perform in Smash4, they could have taken the chance to make Ganon accidentally too powerful for a while to see what works and then dial him back slightly, instead of just making him poor every time.