Ok so let’s say we got 6v6 in Arcade and people actually noticed it. Generally the only people who would be playing it would be the players who insist 6v6 era Overwatch was perfection, which is now only a very small portion of the community. They could reduce tank health a bit and remove role passives, but they can’t bring in old abilities because the new heroes will be misery when alongside that. I mean, imagine old Orisa and Rein vs current Junker Queen and old Roadhog. Double shield will come back, thus invalidating a LOT of the roster for not breaking both barriers fast enough and not killing tanks fast enough. It’ll be harder to keep both tanks alive too since you’ll go back to supports both having to worry about a tank each, which is awful with some support comps that work with one tank like Kiriko and Lifeweaver.

But even without making heroes work like they did in OW1, 6v6 would still be really bad with how new heroes are designed. Tanks rely far less on needing armor or barrier than they used to, and supports don’t need to rely so much on having massive healing output as much as utility as they used to.

If you had Rein, Zarya, Sombra, Sojourn, Ana, and Baptiste vs Junker Queen, Mauga, Reaper, Cassidy, Kiriko, and Sojourn, the latter team will lose. They’ll struggle against barriers, Zarya will feast from bubbling Rein, Sombra can harass the supports struggling to keep both tanks alive, Sojourn can harass the supports and DPS from a distance, and the supports are basically the only good two for healing a couple tanks still. So many characters would just be terrible to use and miserable, likely especially any future characters added.