Would also expect them to become more scarce if Colonisation supply is basically just mini CGs.Did they ever happen every thursday? I don't remember that being the case for as long as I have played the game (a couple of years).
Community goals are rarer nowadays, but they aren't completely gone. Usually something needs to happen for them to create a CG out of it. It appears to me that they don't tend to create CGs that don't really do anything anymore (except perhaps when there's a lore reason for them, such as helping the victims of a natural catastrophe on some planet or something).
I think the "weekly CG" has kind of been replaced with Power Play 2 weekly tasks. They are somewhat similar in that you are tasked with doing some stuff (more diversified than typical CGs), and there's even a leaderboard and you get a payout depending on how you place on that leaderboard.