Especially in normals ive noticed this to be the case. Wins and losses both feel like stomps 80% of the time and 1/5 games max feels like its actually pretty evenly matched.
Its really dumb, winning super easily with all lanes dominating (kill and level advantages) or losing in the same way just feels really crappy.
Although I personally think its in large part due to the holiday season, a lot of casuals who don't play regularly have free time and are playing right now, because they don't play that often their MMR (whether normals or ranked) does not match their skill level so they get put into games that are either far below or far above their skill level and either stomp or get stomped.