Keith, actually people are being more open to saying that the matchup is even on paper. Peah's dash attack and turnips are mad strong against Marth, but peach really has to choose her approaches carefully to not get outranged.
I have a lot of mental theory against peach which is why I'm not really nervous against her. Jr, u said u don't really realize what u did right of wrong.. this is because peach's bait and punish game is actually not that strong, but her trades/attrition game is soooo good. So losing to peach is usually due to technical errors on our part, not knowing what is safe against her, and LOSING TRADES. She mainly loses to superior mobility, which actually very few characters can do, namely fox, falcon, jigglypuff, and maaaybe pikachu (though peach can win mad trades with pikachu if she realizes his game plan.) Peach has options that will outprioritize everything, even against Sheila and Marth who try to play safe. Nothing is safe against peach, so u have to try to bait her into doing something laggy, like dsmash or dash attack, or outspace a float cancel aerial which is hard because she has 0 frames of lag. I think we get frustrated due to stupid trades, sometimes we feel like we have to approach her. We kinda do, but we just gotta keep our head in the game and adapt constantly because she has options for everything. She is a big ball of priority, but slow moving. She is able to pressure every character with trades except jigglypuff.
Perhaps she can't really trade with zelda and Gabon but those characters are freakin slow and have to deal with turnips
In theory she can also lose to suuuuper gayness, like a dedicated needle camping Sheik (ntsc needle grab dthrow!) or a strong young link that chooses his camping methods well. Puff beats her bc puffs hair ***** everything peach has. Basically if a character can avoid her and not trade anything, she can lose... But I don't see that being realistic for most characters lol. If I was to choose a character to fight her with, id personally pick fox myself. Pp and mango have shown that beating armada is possible with spacies if u play legit and outplay her, but armada is just so excellent with that character.