Sure, not every shoe brand is equal, but if I know I'm a 9, I can generally start there and find a shoe plus/minus a half size. I have yet to go into a store and wind up in a shoe that is 3 sizes larger than what I thought my size was. Or 3 sizes smaller. Or a size 8 in one shoe from a brand and a 10 different shoe. I can order Nike/Jordan brand shoes without trying them on and they fit. Have done it for years.
I went to re-buy the "same" jeans ~8 months after my initial purchase and the size I was wearing didn't fit in the new jeans. Tried another pair with a different wash and was back to the original size. I have tried on jeans from the same brand with similar cuts and came away two sizes apart. I can swing several sizes as a starting point between some stores. I get it, not every jean is going to be identical, but it isn't a ridiculous ask to be able to have a size I can start at and be within a size of what I need.
I went to re-buy the "same" jeans ~8 months after my initial purchase and the size I was wearing didn't fit in the new jeans. Tried another pair with a different wash and was back to the original size. I have tried on jeans from the same brand with similar cuts and came away two sizes apart. I can swing several sizes as a starting point between some stores. I get it, not every jean is going to be identical, but it isn't a ridiculous ask to be able to have a size I can start at and be within a size of what I need.