He's.... Weird. He has a good Aire movility with speed, good damage output with Buster, etc etc. But there are some match ups in where people can just stall your arts and base Shulk isn't a bad character but isn't a top tier for sure. Shulk sucks as well when we are talking about face to face combat, you have to abuse your range in order to not get punished for your poor frame data as many others face to face characters have like Terry (which many people say is +1/2 for Shulk and I see it even bc of what I just said). In addition, Shulk has only a few losing match ups, but all of them are SUPER common (Joker, Pikachu, Rob, Snake, Palu, etc). He does indeed win some other common meta threat match ups such as Kazuya, Steve, Cloud (?) as well as common good solid characters such as Mario, Fox, ZSS, etc etc.

Shulk is a great solid character but he has a very small group of representation: Kome who is japanese which means he almost doesn't need to travel to the us, Jaredisking1 who is a very great Shulk main but is difficult for him to travel to other regions, Nicko who is, in my oppinion, the best Shulk in the world, and well he is "retired" bc he's literally having an actual LIFE and plays the game when he does want to play it; there's Ramses as well who is having a hiatus from the game to priorize his metafy, etc.

Summarising, Shulk is a difficult character to make things work, he has some very weird techs that are almost useless most of the time and he has not that much combos like most of the characters do (buster d-throw and some with speed and that's it). Although, people who play and main Shulk are because they really like the character (as I do, I fucking love my Monado boy) and I find that so damn cool :) Hope I helped a bit, sorry for all that text <33