Olimar is easily top 15. Results say otherwise but he's a character who some people honestly won't put the effort into. Shuton has proven that he can be solo viable at the top level, even if we don't see him much in the States.
Fox is outright bad for him, and while I don't think it's a bad losing matchup, Sonic is obnoxious and often not worth the effort it takes to play. Otherwise he goes even with all the top tiers at worst. In lower tiers, Corrin is quite difficult, but can be camped out, Peach and Yoshi's excel at attacking from his blind spot, and Wario is potentially a tough fight as well. I've always had issues with the Greninja matchup, but Shuton does fine in it so it can't be that bad. Otherwise he has very few losing matchups.
Olimar has the obvious issue of low priority aerials, but his frame data is good enough that he can make them work for easy whiff punishes. The man has highly damaging combos, virtually never has to approach unless he wants to, and has the capacity to outplay all other zoning characters. He excels at controlling ground space, has no stage he doesn't really want to be on (bar maybe Dream Land) and has better kill power than the rest of the projectile specialists (unless we count Link). His boxing game is actually decent with a quick jab and D-tilt, and these are both options that have guaranteed followups until high percents. He boasts an admittedly situational kill confirm off of Red and Yellow grabs, a solid kill throw, fairly deadly smashes and the awesomeness that are Purple b-air and up-air. His F-Smash is among the best grounded spacing tools in the game, Purple Pikmin are among the best projectiles for walling out opponents, and his range basically makes him a sword character... or at least more of a sword character than Toon Link or Metaknight.
He carries a few flaws, namely the low priority on aerials, no hitbox on his recovery, bad OoS options, light weight, and a fear of reflectors (that people often overhype). Beyond that the character isn't lacking anywhere, most of his flaws are easy to hide, and his matchups are actually quite good. The character can switch between camping and aggression very easily, and that makes him more dangerous than most characters.