Part of the trouble with casual matchmaking is that so many people have played the game for so long by this point that there aren’t consistently enough people A) in low skill brackets B) with low enough ping to be playable C) searching for games at the exact same time you are. Since that’s the case, it doesn’t have much choice but to dump you into the best game it can find, and that’s all too often going to be a game chock full of people in the middle skill brackets. Fortunately, casual doesn’t penalize you for leaving a game early, but it does still have an annoying propensity to throw you straight back into the server you just left which kinda defeats the whole point.
Also, rank is by no means a reliable indicator of skill, as many smurfs will run rookie or semi-pro accounts despite having hundreds of hours in the game on another account or platform (or someone will just be kinda bad at the game with hundreds of hours, getting promoted into the higher ranks by sheer dogged persistence). Ranked tends to have a better matchmaker from what I’ve heard but I just play Rumble most of the time and so I don’t mess with anything formally competitive.
So, I know I just wrote a whole lot that doesn’t really fix anything, but it’s just a quirk of the matchmaking functionality when the game isn’t on sale (with an associated influx of newbies all at the same time) or a free weekend (bigger influx, only temporary).