That's the reason Peach's have such a hard time against Snake. Snake is even more defensive than Peach. His tilts don't work when he's moving, so it's much better for a Snake player to litter the stage with traps and get you to come to him. The difference between Peach and Snake is that, thanks to the Snakedash, Snake can continue being on the defensive WHILE ATTACKING. Snakedash into your opponent and defend yourself with usmash while you slide and then start tilting. It's a vicious combination.
Unlike Meta, Snake's got a LOT of open spots that can be exploited if you figure out his defensive pattern and alternate between aggressive and defensive play. Play defensively till a hole opens up and then go extremely aggressive. Why do I say extremely? Because once Snake's in the air, he's at a huge disadvantage and you have to exploit it as much as possible before he gets himself settled and still on the ground where he can tilt you.
I do agree that Snake's KO power is very frustrating compared to Peach's lack of it, but Peach can combo Snake very, very well and get that damage up fast, and he IS gimpable in a non-traditional way.
I'm going to write a Snake guide at some point I guess. But some main things to pay attention to:
1) Peach's Bair erases Snake's usmash. If he Snakedashes and you're short on time, Bair it. It'll erase the missle and knock him out of the Snakedash.
2) Peach's Dair will pull Snake out of a Snakedash if used right, and Snake is VERY easily combo'd. I can do ~40-50% starting damage on Kamaji if I get him in a Dair initially. Dair is your best friend in this fight, and easily your best approach (or float to Fair).
3) Peach's Fair is excellent for Snakes who erect a usmash wall (constantly usmash). As soon as a Snake usmashes, learn the amount of time you have, jump in their and hit him with a fair and back out before the missle lands. Do it ASAP because after he ends his firing animation he can utilt you into the missle if you get too close.
4) Once you get a Snake off of the stage go crazy aggressive. Don't necessarily chase after them but rain turnips off of the stage. The moment a Snake up-B's they are INCREDIBLY vulnerable to Peach. Peach's fair knocks him out of the up-B, and the Snake can't actually attack you back without dropping the up-B and not getting it back (thus dying), so he generally has to just take the hit. Throwing turnips will keep him from getting back with his second jump and force him to use up-B, at which point you chase after him and do as much damage as possible (or grab him if he passes a ledge). Kamaji figured this out fast and always recovers high, but then I can engage him in the air as he falls. Uair to Nair works pretty well- if he aerial dodges the uair the nair gets him.
5) Remember the grab trick! Grab snake out of his up-B on a ledge and let him get out on his own without doing any damage.
6) Send every uncooked grenade back at him. Cook the grenades yourself if you have time. It'll make him think twice about using grenades.
7) Snakes expect you to be afraid of their C4. Don't be. While you shouldn't stand on it alone, if Snake's using it as cover just dive into it. He's not going to blow himself up too and you can always float over the C4 or air dodge when he goes "NOW". They're often thrown for a loop if you aggressively dive past the C4 and pound on them because they expect it to give them some breathing room. Instead, KEEP the fight by the C4, throw the Snake at the C4, and keep him in the air as long as possible.
8) KEEP HIM IN THE AIR. Snake's going to try to land as soon as he can, so take advantage of that (dash attack him right before he touches the ground, for example). As long as he's in the air, you have the advantage. Just don't get so aggressive that you jump in front of his Fair and get spiked.
9) Turnips. Use them wisely, but don't abuse them. Snake punishes the glide toss with his ftilt way too easily so don't glidetoss into his face. Throw turnips at range when he's playing defensively, then switch from turnips to aggressive mode when he makes a slip. Once you get him off a ledge launch turnips like a madman to force his angle of approach and make him come on low so you can get a good shot at him when he up-B's.
10) Go for the gimp kills. Grab him out of the cypher, or keep Fairing him out of the cypher till he can't make it up. You may or may not knock him off the side but you can prevent his recovery over and over till he falls off the bottom.
That's how I do it, anyway
Hope it helps someone.