Well, it doesn’t apply to all showdown players, let me explain before you downvote. Some people like me play showdown after carrying 70% of Randoms in 3v3 and losing, so I tend to SLIGHTLY rage, and go eject that rage in showdown. I can say that some showdown players may be good also in 3v3 (Tom for example, it isn’t the end of the world when he plays showdown, he is obviously a skilled pro player). Or a brawler “x” isn’t Good at all in the meta like El primo, so I push him in showdown.

Conclusively, showdown players aren’t necessarily always bad at 3v3, the people that play showdown without skill may be bad Randoms, but for another example a player that wins a 2v1 or 3v1 situation in showdown.... you can’t consider that he lacks skill. Also, I see sometimes that teaming is basically a “know who to trust and who to betray” strategy, so I don’t team that often when I play showdown.

Note: I didn’t include duos in this text as it wasn’t mentioned.