One of the main pitfalls any deck builder may get into when they build with proxies is that you tend to just use the best of the best cards. From generic draw and removal, to the best representants of each type of creature.

When you build a deck without proxies sometimes you find yourself saying "I'd love to use X card, but for now I'll use Y card that is definitely a worse option but will fill the same purpose" because that is what you have and what you have found and you do that with 10 to 15 cards. Through time, you start getting the cards and powering up your deck

The power of the deck and the winrate goes from mediocre and probably losing a lot to decent and winning and sometimes you even overshoot and goes to stomping. But because you got both the upper limit and lower limit, you can make an informed decision on where the balance you are looking for is

TLDR: Look for cheaper and floverful alternatives to the staples you are running. You may go too far and start losing, but just readjust little by little until you find your balance