Shulk is suffice to say, okay. A Fire Emblem character would still be a better pick than him.

His normals are pretty decent, and his Smash attacks are also of fair power, especially during Power mode. He actually does a lot of damage (not as much launch though) in Buster mode, but since these modes only last temporarily, players can very easily play against those and make them useless, otherwise he'd actually be pretty damn strong if he were able to keep a mode until he changed.

His Back Slash is pretty unreliable as recovery (in fact it's absolutely horrible) but it can be used as an aerial approach, and has very good range. The bonus attached to it where he does extra damage and launch if the opponent has their back turned is not to be counted on, but if you do land it, it's noticeable and pretty strong.

His Counter has around the same frames as Marth and Lucina, but it's kind of a rush slash counter instead, so it can miss if the enemy attacks from a weird position.

His Up B is actually very good for launching and getting kills, especially with Power mode and if they're high enough (around 100% should do it most of the time). Although all the launch is in the 2nd slash. The upward slash can catch opponents, and 9/10 times you'll be able to follow after that with the 2nd slash.

His aerials are a very linear hitbox if he's attacking in any direction other than forward (his back A and up A are a stab, and so is the down A). His neutral air A is pretty good for crossing over players, as it's an upward slash and will hit very early in the swing. On ground you'll find yourself using the AAA most as well as down A like most sword characters.

Basically, Shulk is okay, but other Fire Emblem characters are still better and more consistent, but by no means is he bad. Just a note, do NOT use his Monado Arts (standard B) while under attack. You can't use any other moves while selecting a mode.