Yeah, I barely use ICs ever.
Jiggs and peach very occasionally (peach in teams mostly).
Edit: looks like pp and zhu have The doc stuff covered.
Some things to add: if you see doc do d-air at almost any given point, you can b-air beside him and beat it easily. Sometimes it may not be wise to contest his b-air, especially at the edge of the stage. A trade may get you gimped if he's at a low enough percent. Most docs will shield a lot, and also try to shield grab you, so you will probably find a lot of opportunities to grab Vs doc. If you're center stage, then u-throw. If near the edge, just throw him off.
Edgeguarding vs doc, always hold the ledge when he gets reasonably close to the stage. Also don't fall for stupid recoveries like his tornado while recovering low. Watch what he does. If he up-bs early then roll on to the stage. If he does the tornado, either refresh your invincibility, or drop down and b-air him (or shine -> b-air/d-air). Just remember that doc can't go very far, and his recovery is limited in that respect. Also, if you know that he likes to throw pills while recovering then b-air/d-air through them and hit him while you're at it.
Edit 2: crossing up doc's shield with aerials can be risky, since his u-smash oos hits behind him. Make sure that you are outspacing it if you are pressuring from behing him. When pressuring from the front, I recommend using double shine a lot. Also beware of u-air oos. It's really fast and hits in front of him (the person I've seen do it aside from myself with either Mario or doc is mango, so you may not have to worry).
Edit 3: kind of optional, but doc kinda gets ***** by a good platform game by spacies. Even going out of your pressure onto a platform is really good (like double shine -> platform waveland). You can try to bait aerials/movement from him and see if you can come down and disrupt him. Picking a good angle to attack from with a falling b-air/d-air/laser is really good. If he's jumping around as well, the. You can catch him with a laser then start a combo with n-air or something. Just beware of u-tilt when you're coming down. If he's walking around underneath, then he's probably gonna go for it. If he's committed to a WD/DD, then there's a chance to attack. Just try not to get tricked.