We still have this atm: the third game Is a game on "neutral" grounds. Tho as anyone ever can tell you: bo1 are notoriously frustrating for how likely a fluke would be to happen.
The idea is too make it so that a player who is slightly better who have 3 neutral ground games to prove they are better than the opponent, rather than each playing their main and then having 1 neutral grounds game.
This is pretty idealistic but there is the wrinkle that it probably means you won't get to play the tier you're best at, for better or for worse. If I qualed I probably would be lucky to play a single game of DOU. Yes that makes me have to play other tiers, but that also means that you'd be essentially disregarding the biggest chunk of what puts each player in contention to be the best tours player. The BO1 thing is a problem and obviously there's no easy fix in this situation, but I do think that being good at Pokemon transcends tiers even if you may be more learned/practiced in one tier, as long as you have a minimum amount of metagame knowledge and are good enough at the game it should be a mostly fair and even format. If you lost in a tier your opponent mains, then so be it, all power to them for being good in that tier. I would say its not infrequent that a mainer loses in their own tier, even in something as "siloized" as DOU appears to be; as long as you put in a little bit of practice you'll still be disadvantaged (which is natural, someone has to have an advantage) but a good player still has a decent fighting chance.