Sizing has SO MUCH MORE to do with how conditioned your feet are. Not like a T-Shirt.
Your shoes are your sabre by your side - unique and personal, tailored, and job-specific.
Some shoes (Miuras, Mythos, Moccasyms) are 15-20 years old. In those days, when you bought a shoe, you bought the smallest size you could fit into.
THESE days, you CAN'T sell shoes on-line if you base it off this model. Instead of making the size of the shoe off the length (like before) many companies now have newer models pre-sized. Meaning, if you are a size 9.5, you SHOULD BE WEARING a 9.5 (the evolv Shaman is a great example, as well as many new 5.10's).
Look, I don't play basketball. I suck at it. I could buy LeBron James shoes TODAY, the way HE sizes them, and probably they will at least keep me sucking as much as I already do when I play. They might even make me BETTER at it.
A new climber CANNOT climb in Chris Sharmas shoes the way HE fits them. No different than a guy who is a white belt walking into a dojo trying to break 15 bricks.
Let your feet get strong, objectively analyze what it is about your footwear that is failing you and how you use your feet (are you always edging, do you bury rubber behind edges, do you wear big shoes so edge with the big toe's first knuckle [bad]). You are your own coach, and you have to have a sample size of Experience - no toy can fix that. Maybe someone who has worn a lot of shoes and knows a lot can fill you in on something appropriate, but at the end of the day it is your feet in them - not mine.