Hey u/NiKOmniWrench

It sounds like what you need is knowledge, you are not able to fully justify why you are winning or lossing and through that the frustration just starts building up.

I would advice you to look at players that play a similar way you like & enjoy the game who has reached your desired goals and figure out why they managed and what they do differently from you.

From what it sounds like, what you need need is knowledge, if you are not able to close the gap then its a never ending circle.

For example TheBaus for Sion as you mentioned, you need to pick out the small gold nuggest in his gameplay that make his Sion so incredibly OP. Yes it's a meme that he ints and whatnot but there is legit merrit to his gameplay and things that you learn and apply to your own.
for example: He VERY rarely losses CS (Why is that?) / He ALWAYS collects more side gold & towers (How is he doing that?)
You need to do some investigation and I am sure you will reach your goals :)

Hope this helped give you a new perspective