Are you viewing competency based on the outcomes of the decisions made or based on the quality of the decisions relative to the available information?
A face mashing Yi could get lucky enough to have his early all-ins get enough kills to be fed so that his subsequent all-ins are a lot more successful, but that same Yi could also go 1-14-2 if the first two kills were able to limp away because they remembered to drink healing potions. Good and bad outcomes can come out of the same incompetent player. The opposite can also be true. I've seen pros die to the raptors, during professional broadcast games.
The MMR system does match players with and against similar skill levels. https://na.whatismymmr.com/BlueSnug Based on your ranking, it would make sense for you to be matched with mostly poor players.
You can focus on your teammates, and get frustrated at their mistakes, and try to teach them every trick you know. Or, you can focus on yourself, learn everything you can from everyone who outplays you even a little. Watch replays, to see where is safe and where is dangerous. Ect.
You spend a lot more time with yourself than with any set of 4 teammates, so you have a lot more time to improve yourself. Also, improving yourself helps you out a lot more than improving a set of 4 people who you probably won't play with again.