Oh this is such a fun question -

The biggest difference is time commitment. Everything was sewn by hand. You can sew basically the same things by hand as with a machine, but it would be much more time consuming, so you would probably choose to opt for more simple or multifunctional designs.

There was a variety of types of materials- heavy, light, wool, linen- but none of it was stretchy. So like a shirt you pull over your head would be a no go. The only type of stretchy material they had was knitted material. Knitting was in fact a new technology to Europe at the time. There were no zippers, and buttons had been introduced to Europe in the 13th century, but many people still wore clothing that laced up in some way. So something like modern pants and a jacket would be feasible to make, if not the fashion of the time, and just without a zipper fly. Many colors of fabric dye were available, especially in port cities like Venice. Also fabric could be decorated with embroidery, but today’s fabrics with printed patterns on them are a result of the industrial revolution. Weirdly enough, the one color you might have a hard time getting? True black. Nothing in nature is really black, so good good black dyes weren’t really available until synthetics came around, so a lot of the black dyes would be more like a dark brown. Plaid fabrics are (or can be) the result of weaving so they would be available. There were many styles of shoes but most of them all had leather soles. So no sticky rubber soled shoes. But frankly a modern fashion designer who went back in time could make a lot of the things we wear today. The thing is tho, I don’t think they would- I think if a modern designer was transported back in time when clothing was more labor intensive to make, wash, and care for, they’d want to make clothing that was more modular, durable, and repairable. Like what people wore at the time.