I mean, even looking at the MUs he loses (and slightly, mind), how many of them are relevant? Cloud, Rosa, Sheik, ZSS, Mewtwo, Falcon.
Of those, we've seen Lucario beat most of them in tournament, multiple times (hi Sheik). Falcon and ZSS are the only two real roadblocks (and I'm not quite sure about Cloud - need to see Tsu vs Tweek going Cloud).
So if we're looking at how his MU spread holds up against the type of bracket you'd see at an S-tier, you'll see Lucario is quite capable of making top 8, and consistently. Very few mid-tiers can say that much.
Beyond that, Lucario's fundamental ability makes all of his -1s volatile. Fox is a -2 because he's in many ways immune to that volatility. He abuses Lucario's frame data, makes him wary of using his top tier projectile, can kill him when he has aura and when he doesn't rather easily, abuses his recovery, prevents him from landing, etc.
Most of his -1s are actually pretty subject to the volatility of aura. That makes them distinctly more winnable for him that most other characters' -1 MUs.
Tl;dr: Lucario's spread has only one, relatively uncommon hard counter. He goes even against most of the best/common characters in the game, and for the instances he doesn't, the volatility of aura allows him a stronger chance than a traditional -1 would show.
Personally, I wouldn't just count "losing MUs" - how bad those MUs are is more important. For example, Leo's Marth MU chart has 10 losing MUs.
