Time of day you're playing has a *huge* impact, at least here on Crystal. If I play at like 2 AM, there's a *ton* of weak players on the field, and it's highly likely you'll get at least some of them on your team. You *can* partially mitigate this by playing classes with high carry potential like AST, RDM, and NIN... but one man can't carry an entire game on their own.
But when I play during prime time (most evenings until around midnight server time), there's a lot more people playing *and* the skill gradient is smoother. You see a lot more of the top 150ish players, a lot more Diamond players (not a measure of skill, but it does mean they've generally played fewer games), etc. Games are much more likely to be evenly balanced, and it's in those games where your individual contributions can shine through because you're less likely to be saddled with dead weight while the enemy team is not.
It sucks, but if you're actually focused on winning/pushing rank, you really can only play (ranked) CC at certain times of day.