In FG All olimar has to do is run away though its so dumb.
All a
bad Olimar player has to do is run away... A lot of Olimar's moves, though lacking range, are really fast and can knock foes sufficiently away. Purple Pikmin can create powerful pressure, and his grab is pretty useful if you know how to use it. It's true that Olimar's main damage tool is his Pikmin, and he has to be more patient, but if you're irritated by patient characters, you're gonna struggle anyway, because there's a ton of them.
His Pikmin aren't even really an issue, they're basically just as scary as Fox's lasers, except you can kill them in collateral damage and they have less range,
and Olimar basically needs atleast one with him at all times to be safe, so he can't even really spam them unless he has multiple Purples. If an Olimar player is just launching Pikmin at you and expecting a win, they're leaving themselves
waaay open. He can't "just run away" because not only is he not fast enough against most characters, he just doesn't have the range to stay away from you. It's true, he can rack up damage from long range, but he can't do anything remotely scary until mid-range. -and often, he has to be pretty close to push you back or kill at all.
As
Yoshister
said, they don't halt your approach (unless they're the Purple Pikmin)... -you just have to not give a crap about taking that Pikmin tapping damage and watch for Purples, then you're basically fine unless the opponent outright outplays you and swats you away each time you approach. The Pikmin are just pressure, not a win condition, don't let them get to you.
It's kind of irritating that Olimar has this reputation at all. It's almost as bad as the "Little Mac is a rushdown character" mentality most people in FG have.