I've been struggling with deck building since I got serious about commander last year. My winrate in proper pods has been abysmal. Only thing that has netted me wins consistently is my cloud deck. I'm not unfamiliar with proxies I've got some cEDH decks that I've netdecked and proxied before but never used it for my own brews.
My decks were designed to be bracket 3 with game changers and intent but factoring in budget and trying to make cards I already owned work with what I'm building I often only built bracket 2 decks that legally became 3 because of game changers. (I get to tutor mid in this awful deck)
I pulled lorehold at a recent pre release and decided to proxy the entire deck due to most cards useful in it being harder to come by or costing a lot.
What an eye opening experience. Now my deck feels like it's constantly going for its win condition in every card I play and has redundancies that help. All by virtue of "I got to pick every card I wanted for the deck and don't have to consider external factors like pricing and if a card is in stock near me". It's become easier to identify the problems with it.
Obviously all of this is "no duh" to many of you. But it's just shocking to me how big of a difference an extra 7 or 8 cards made. Removing all those external factors that were subconsciously influencing my decision making changed things. I highly recommend you do the same if you're struggling with deck building.
(It also probably helps to have a commander that does something very specific. Lorehold being such a narrow effect but with such huge benefits made it very easy to design for)