The biggest problem is not people are factionalized, because that happens in any movement, but that it takes a long time for people to work out their differences, overcome them, and maybe establish new differences to work out later - that's a decades long process. The right began doing it in the 50s and 60s, before taking power with Reagan. For the left, if there's any ambition to do the same kind of thing, with Trump in power you don't have any wiggle room.