The three teams just creates a dynamic where the losing team can throw for whichever team they like. I prefer my matches end with the most skilled team winning the game. That doesn't happen in a 1v1v1 setting. Just look at half the matches on seal rock without premades. North spawn, or South spawn teams get camped and farmed at their spawn points and they're denied the ability to even capture a single node for several minutes that effectively seals their fate in third or second place without the intervention of RNG spawning nodes right at their doorstep. Even Onsal is guilty of this happening as well, though unlike Seal Rock the node spawns are at least loosely balanced and defensible between the teams.
Three way PvP is not a good idea if you care for competitive PvP.
1v1 PvP has always been superior, and if one team is getting slaughtered, they lose the match and it ends quickly for them. There is a reason the vast majority of PvP games are 1v1, not 1v1v1. If you want your comeback in a 1v1 setting you better work for it and not hope that one of the other 2 hostile teams throws for you.