Where are you getting that from? It seems to be fully supported: https://caniuse.com/mdn-css_properties_aspect-ratio
I've been using if for months with no issues in cross-browser testing, and I haven't enabled any experimental flags.
I've been using if for months with no issues in cross-browser testing, and I haven't enabled any experimental flags.
So basically not supported, and you have to go back to div hell.
There should be some future.js file that you can import to make all this stuff just work in older browsers.