Last time i checked the Generation Banlists didn't work and I tested it enough times... People who had XYZ and Pendulums could enter for some reason. I told that to a few mods in Discord and they confirmed it. There was some kind of bug... I don't know if they didn't reported it yet or it has been fixed. I will check it...
Still, though there are a bunch of problems with the Default Banlists...
For example, there are a fair amount of cards that are considered "broken" especially in DM Format, the game gets dull and focuses around specific cards which results in turning DM Format into Goat Format! Do you get it? So the only solution is to make hosts able to alter the Banlist or use their own Banlist...
I know that a lot of problems that i haven't yet consider will occur but in the current state it's not very practical either...
Also, we can't just ban the broken cards, because other broken cards will take their places eventually...
In addition,
1) We may need a lot of time to create a banlist, but you do it once. You save the digits of each card and just copy paste it... You don't need to do it all over again every time.
2)They don't need to read anything, there is a notification that says which banned cards are included in your deck. It may take a bit to adapt their Decks, but mostly the banned cards will be common broken cards like i said. We won't ban the half cards that are available, they are mostly specific cards that are prospective. Finding a another opponent in the meantime, I don't see anything bad about that, it's not your fault that their deck happened to have those cards. LOL