What doesn't it compete on? Model 3 is much quicker. Beauty is definitely subjective. I don't love the Model 3, but find the Ioniq quite ugly. They compete on price.

Build quality, Model 3 is not "much quicker", Ioniq has a higher range, customer service, interior design, better colors

Model 3 performance is 3.1 0-60, Ioniq 6 performance is 5.1. That’s pretty big. On the low end model 3 is 5.8 vs Ioniq 6 is 8-9 seconds, also much slower.