So you just finished a comp game of 6v6 where you could pick 2 winston 2 tracer 2 mercy if you wanted? Man I must have missed that game mode or it doesnt exist because Blizzard patched that out of ranked and left it to not exist anymore and the only way to play it is in an unranked arcade mode that may or may not be available on any given day because a patch took away the classic Overwatch ruleset.
Meanwhile I already said why Left 4 Dead fails as an apt comparison to Overwatch. It is not only an entirely different genre but it is built with an entirely different model in mind. L4D is built around the idea of a buying the game playing it for awhile with friends but in 3 years you are playing something else. Whereas LoL, Overwatch, Apex, Valorant, etc. are all built on the live service model where you are expected to be playing it 3 and 5 years from now and the game is constantly expanding to keep people happy. So the games are built under entirely different premises and therefore your comparison fails.
I would love to know though (though again I know you cannot) if you can find a single non syntax reason that the huge LoL patch that updated the engine, changed the core gameplay and altered the monetary model is different from the OW2 patch which will update the engine, change the core gameplay, and alter the monetary model. Oh and you cannot play “classic” LoL. I found the flaw fairly easily in your example and await seeing if you can find a non syntax one in mine (because calling it something different doesnt change what it is).
Meanwhile in Overwatch right now if you want to experience those other game modes from the game’s past you are stuck hoping that either an unbalanced unranked Arcade is available for No Limits, or for Open Queue queueing for an unbalanced game mode that if you play ranked has no one playing it.
So if your sum goal is a random unbalanced Arcade mode that may or may not be available (as is the case for No Limits) I suspect that is something that they could trivially do as they are likely not going to remove the optimization tech they have for 6v6 because keeping it in place solves some technical limitations they ran into during the Overwatch cycle (the most well known being the issue with Echo’s ultimate where the chosen player cannot switch heroes while it is in effect).
Again though given that OW2 is comparable to both the No Limits removal patch and the Open Queue removal patch an arcade mode, though the maps would still be in 5v5 form, is about all that would be expected. Possibly also a 2CP Arcade mode but that would likely not be for about a year after release so that nostalgia can kick in for people who miss those maps.