Luigi is as good as your opponent wants him to be.
if the guy sucks at DI.....doesnt know what to do when you bust out that crazy wavedash....and doesnt know how easy it is to edgehog luigi...then luigi can do pretty dang well. there is a reaons some people think luigis recovery is amazing and others think it sucks. its because some people know how to edge gaurd and others dont ahha.
now if your playing somebody that knows how to propery camp luigi, properly gimp luigi, and properly combo luigi your gonna start getting pissed off that you play luigi.
Ehh, that's not entirely true now. While camping, getting gimped and and properly comboe'd are all pretty hard to deal with, it's still possible to make Luigi a tough match-up for the other person. Definately not easy, but possible. You just have to apply everthing Luigi has. (Emphasis on everything)
There's always different ways to deal with all of that stuff. Some more ways than others though.
I mean, let's look at camping: Against a Falco, all you have to do is learn how to powershield like 1 in 10 lasers, (which is easier than people think) and then approach the Falco as fast as possible, and then stick to him with every aerial and jab you can muster until he gets hit/grabbed. For Fox, do the same except you have to be more patient, and always try to wait for the slightest chance of an opening. Against Peach, catch her turnips unless she's baiting you into an attack. It's as simple as that. Catching turnips is about 3x as easy as powershielding, btw. If she's camping, chances are she's not going to be baiting you. And you have to take advantage of that.
Against getting gimped, you just
have to make sure you don't make some move that was only half thought through, which gets you killed. You may even find that you often have to make a move that will give you punishable lag, but I assure you it's better than getting gimped. And of course, it may sound a bit harsh, but you really have to
always make sure you have the tornado recovery, and you have to be able to
do the tornado recovery.
As for getting properly comboed, the only characters that can make a big enough difference in the match by those combos are the ones who get comboed and ledgegaurded/tech-chased easy themselves. You just have to make sure you don't miss any of those opportunities to do so.
Soo...basically, you have to play very near perfectly with Luigi to deal with those things. That's just how it is.