Please note, you may want to edit your starting post. Use of covered expletives is not permitted per the forum Code-of-Conduct.
EDIT: I see you have updated your post, thank you,
I feel your frustration, but I do encourage you to try to use the looking-for-group tool if you are looking to have more consistent games.
There is a GREAT guide to the matchmaker here. But in short the hidden MMR of non-Competitive modes are not dictated by your Competitive skill rating. It is perfectly reasonable and expected to find players of a higher competitive rank in arcade modes.