I know Yoshi pretty well actually. I've run into him in tournament far more than one would expect, and he is definitely the single campiest character in the game. Olimar is probably #2, but I think Yoshi edges him out. Yoshi spams eggs and pivot grabs, and if you get in his face where that's not going to be an option, he abuses his ridiculous jab to just run away. That's how every good Yoshi I've ever fought has played, and it works. His other moves are things he mixes in when the opponent makes a mistake in navigating around his core three camp moves (Egg Toss, pivot grab, jab). Like, if the opponent jumps in past an egg and lands in certain positions, dash attack is good. Running up smash sometimes even works like that. Just doing a jumping Egg Lay can be great disruption too, and your tilts can provide assorted small levels of trickery. In Bbrawl, dsmash actually is a really nice thing to consider more often even. However, those are the "extras" on your game. The core is extremely hardcore camping with Egg Toss, pivot grab, and jab. Yoshi pretty much doesn't shield; he just keeps you away so effectively that he barely needs it. Yoshi's aerial acceleration isn't really very good (even though his top speed is so high), and quite a few characters easily outrange/prioritize or even just outspeed his aerials so I don't think playing similarly to Wario is a good idea for him at all.
The comment about Snake isn't even reasonable. In standard Brawl, Snake is obviously a much better character than Yoshi, but he doesn't camp nearly as much. In quite a few matchups, Snake does things like walk up ftilt or walk up utilt. Snake is good primarily because of just how much raw power he has on stuff. He can use some other good stuff he has to have a pretty good defensive game, but it's not like all Snake has going for him is defensive play. Yoshi, on the other hand, is a character for which I have never seen any evidence of a reward for players doing anything other than the most extreme forms of camping. However good or bad Yoshi might be doesn't really change that reality. Yoshi's optimum playstyle is a more defensive playstyle than the optimum playstyle for any other character.
Now imagine Yoshi with a normal shield. He still does this actually very difficult to get around camping game. Once you get in and have your hitboxes out, he can just throw up his shield now. Remember Yoshi has a 22 frame spotdodge so he instantly has one great OoS option (his silly shield dropping animation makes his spotdodge seem artificially worse than it actually is). The campiest character in the game gets even campier, becomes unbearably tedious to fight for large portions of the cast, and probably becomes borderline impossible to fight with anyone slow. In terms of polarization, he'd be very similar to Olimar at that point except probably even more polarizing.
This probably sounds like a very mean analysis of your character, but I'm just being honest about it. I'm not passing judgments on the Yoshis of the world for picking such a campy character or anything, and if you are using him, I just expect you to play to win and camp your heart out. I mean, I can see in Yoshi vs G&W you have two options. You can use eggs to counter my aerial approaches and space pivot grabs and do all that to keep me out, or you can let me in and get wrecked by my turtle beating out your entire moveset and my kill moves being way more powerful than yours and all that. There are no hard feelings about Yoshi choosing what wins here. It's just that it's important to be honest about what wins with Yoshi, and if we're looking at changes to him, giving him extremely higher incentives to camp is just obviously a really bad idea.