You're being ridiculous.
According to your argument Fox has the ability to just get into Marth's face - a borderline high-tier character who excells at mid-range spacing - for free and do whatever he likes there. That makes virtually no sense. Fox can't just approach and harass Marth for free. No character can. Sure he kinda destroys Marth
once he gets there. But there is still the other half of the matchup where Fox has to get there. And that half is a lot scarier against Marth than against Lucina. Enough to make a +1 difference? Yeah, I'd say so.
I also doubt that you are in a position to call out anybody, especially somebody you don't know, for 'doing it wrong'. What are you placings at tournaments? What are your experiences vs high level players? What are the best Foxes you've played
? You can't just call out people for doing things "wrong" when you clearly don't understand how it's done
right.
If you can't accept that the tipper makes Marth that much a better character than Lucina and that there are specific matchups where it can have a dramatic impact - vs Fox is one of them - then that's your problem. If you want the reason it's right here: Marth has a tipper, Lucina doesn't.
Not sure what to tell you if you think than Fox can just break Marth's zoning with Dash Attack other than that you probably have no experience in the matchup. Dash Attack gets eaten alive by side B. It's not a good option against either character, especially not in neutral.
It's not easier for Marth to "space tippers" but how is that relevant? Lucina doesn't even have a tipper. A random tipper fair or nair happens in just about every game, even top level play. That stuff just scares the **** out of Fox.
1.) Lucina fsmash can't kill Fox "as early as the mid percent ranges". Marth's can.
2.) If you hit Fox with fsmash as he's weaving too much it's probably at tipper range. Massive point for Marth as he can kill at 70ish percent depending on range. Against Lucina he'll survive that.
3.) Fsmash isn't the most likely move to hit against Fox, with or without tipper. Random ftilts, fairs, nairs and side B are the tools to look out for - all of which have quite powerful tippers that will kill Fox in situations where he'd survive non-tippers.
It's only complicated if you're not willing to accept that Marth is just the plain better character and that the tipper is a huge factor for that. Just because it's simple reasoning doesn't mean it's wrong. Ask any given high- or top level player of a character whether they'd rather face Marth or Lucina. At best they'll say that they don't care because it's not a big difference, most of the time they'll tell that Marth is scarier. They'll tell you that tipper is the main reason for that.
And they are right.
Marth is better than Lucina.
In virtually every matchup.
...
Because of tipper.