It's not as if web developers like supporting broken, outdated browsers. It's done because without the users using those browsers, the business would be worse

It's not as if web developers like supporting broken, outdated browsers. It's done because without the users using those browsers, the business would be worse off. There are lots of intermediate steps like warning about an inferior experience, but at this point it's necessary to test most websites on at least a few versions of IE9. I've found that using react I've had very easy compatibility with older IE, etc. The only thing I've had to do is install a polyfill or two.