i completely disagree with this post because i believe that it all boils down to skill and tier lists don't mean stuff when it comes to skill
hypothetical: ganondorf is absolute top tier whilst villager is considered to be absolute bottom
player 1 is stuff with ganon, but plays him anyways
player 2 is villager's main in which he has had many hours of experience with
who's going to win? 99% chance that player 2 will win, unless player 1 accidentally does something that forget's player 2 in the ass
like ultima said, it's not "low tiers never bear high tiers"
it's about the abilities of the character when played at an equal skill level
plus, skill isn't everything.
skill can overcome your character's flaws to an extent, but some characters are just more rewarding for skill
plus, you need to account for things like "how does this character fare against others" and "how do different stages affect the character and its matchups"
and some characters have randomness to their moves
you're half right with this
tier lists would have to test each character vs each character to see which one is disadvantaged against the other between top-skilled players
again, skill is everything
which is what they have done, because tier lists are based off tournament results
and again, other factors beside skill are character matchups and stage picks, and your character's own flaws
like, let's talk melee why are roy and marth so far apart on the tier list? what if you could learn to play Skilled Roy? surely tiers dont exist??!!
well, for starters, marth's floatiness compared to roy gives him the edge in comboing and escaping combos. roy cannot even attempt his dair off the stage or he will die. roy's faster falling speed also leaves him more susceptible to combos, i believe
marth's dair is a powerful spike (in the NTSC versions, anyway) that can be easily comboed into. roy's dair is unreliable, a meteor smash (so it can be meteor canceled) and is hard to hit without SD'ing. and i dont think it can be reliably comboed into.
what about their different sword properties? well, marth's sweetspot is on the tip, so roy's is easier to hit, right?
well, being close up also means your opponent can hit you. marth's sweetspots are safer, and he has the tools to keep people at that spacing (unlike smash 4). plus, roy's sourspots are abysmally weak, and probably don't even combo well until high percents. marth's sourspots are more powerful (they can actually KO), and some serve comboing purpose.
back to recovery. marth falls more slowly, so he can get more horizontal endurance. plus, the side B will stall him in the air longer
roy falls pretty fast, his side B isnt as effective in stalling, so he ultimately can't survive off the stage well
marth's up B is also more useful. the one powerful hit can be used as a combo finisher or a surprise hit. roy's multi hit up B deals fixed knockback, and the first hit will only KO the lightest characters (and i think you can DI out of it)
in the end, spending the same amount of time on marth would prove far more useful than roy. you would need significantly more skill/effort to win with roy
there's a lot of things that make roy objectively worse than marth, just check
http://www.ssbwiki.com/Roy_(SSBM)#Differences_from_Marth for a more detailed list
perhaps later i will talk about a smash 4 example that you would have more experience with
also this is like the sixth edit but if there are any errors i typed this at 1am on my phone