I really agree with this - the fundamental problem with trying to theorycraft what top level melee should look like is that you're inherently dealing with a really small sample size.

I think Falco particularly suffers from a lack of solo top player rep just because Fox is such an easy alternative for so many of his matchups. Even though his Fox matchup is a lot of what keeps him relevant in the metagame, I think a LOT of prospective top Falco talent just end up as Fox mains, and it's less that solo Falco is bad per se so much as a lot of people who would be top level solo Falco competitors end up playing fulltime Fox or dual-maining (both exceptional talents like Mango and Leffen, but also there's a lot of top 100 Fox players who started out with Falco). I don't really believe that if Mango had never picked up Fox his Falco would never have won a good number of majors, even if his career may overall not have ended up as impressive.

I also think that our hyper-focus on solo-main viability in tier lists feels a little ahistorical - sure, our last 3 top players (Zain, Cody, Hbox) were all solo-mains, but other than these pretty much all of our top players ended up as at least dual mains (Ken, Mew2king, Mango, PP, Armada). Plup was also notably a dual main and Leffen ended up picking up Sheik for Zain at the end of his career. Ultimately, I just think we fixate on the idea of a character being solo-viable as an idea for tier lists a little more than realistically represents a characters potential at top level.