Etsy's help pages list minimums; seller forums are full of people whose photos still came out cropped or fuzzy. The gap is because Etsy resizes and re-compresses whatever you upload to fit its layouts — and its general-purpose correction "isn't ideal for every single image", in Etsy's own words. The fix is giving Etsy an image so close to what it wants that its processing has nothing to break.
Aim for at least 2000px on the shortest side for listing photos — enough for the zoom feature without visible softness. Thumbnails display around a 4:3–ish crop in search, and gallery views lean square, so compose with the centre of the frame carrying the product: anything critical near the edges is what gets eaten when a crop happens. Keep files under about 1MB where you can; oversized files just give Etsy's compressor more work to do badly.
Every resize is a resample. If you upload 4500×3000 and Etsy displays it at 794px wide, the platform has thrown away 80% of your pixels using a fast, generic algorithm. Doing the reduction yourself — with high-quality resampling, to a size near what's displayed — keeps the sharpening decisions in your hands. It also means what you see in preview is what buyers get.
Keep one high-resolution master per product. From it, export a 2000×2000 square for Etsy, then platform-specific sizes for wherever else you post — Instagram, Facebook, Pinterest each want different shapes, and letting each platform auto-crop a square is how product edges vanish. Batch this once per product, name the files by platform, and reuse forever.