Most of what I saw wasn’t encouraging Stepford/Disney saccharine positivity nearly as much as it was encouraging basic decency and politeness in day to day interactions, including those with groups that traditionally hadn’t enjoyed that. It didn’t even discourage arguments but rather emphasized being productive with them — in other words, argue to find solutions, not to stoke each others’ emotional bonfires.
If anything based on the steep decline in basic decency in the past couple of decades, I think it could be argued that the messaging of the 90s was unfortunately a failure.
I don't think they could avoid each other, given that they're trapped within the same reality. If anyone manages to fork the simulation into multiple branches strictly divided by tribe, will they be happy places? Or will new factions form, and the process repeat?
This is one of the core ideas behind prof. Jonathan Haidt's book "Coddling of the American Mind". There's probably something to it.