For the most part, YL's MU's are all about camping. However, there are different ways to camp. If the person is more defensive, then the best option is the play defensive as well and camp them up harder. If they are SUPER campy, then you can actually play pretty aggro and get away with it by rushing them down and pressuring them a lot. Keeping them from using that shield with bomb juggling off the shield. Young Link can shield pressure most characters very well. In my opinion, he has the third best shield pressuring abilities in the game(next to Fox and Falco) because of his ability to catch bombs off their shields with ease and rethrow them quickly.
If they are playing super aggro and are pretty fast, then you're camping style suddenly becomes setting up traps for them while they chase you around the stage(Example: Have them chase up up on a platform and while their coming up on it, drop a bomb on their head). That alone can be pretty fun.
He is so fast and mobile. He has plenty of options.
A couple of more random perks:
Although he can't kill very easily, Young Link is actually one of the best characters in the game for racking up damage the quickest. His normal BnBs do up to 30-40+ damage just from a couple of hits(Bombs = up to 15%, strong boomerang = up to 19%, n-air = 12%? Plus you can juggle floaties with n-air alone 3 or 4 four more times, etc etc).
In teams he is a great stock tank and works well with someone who can kill easily(since well...YL can't kill lol but racks up damage fast) as long as you camp and keep them from hitting you much.
He has very good match ups against a couple of top tier characters that most other characters WISH they were good at(Namely Jigglypuff and Peach).
Aggro Young Link does work. You just have to be careful since his normals are slow compared to other top tier characters. Watch some Jash videos for aggro Young Link gameplay.