My guess is that most of us have Babel in the mix of a production deployment, in which case I think the “20 year old code isn’t vanilla” loses some of it’s effect.
0: https://www.statista.com/statistics/272697/market-share-desk...
But yeah, I absolutely push modern JS out to prod, because our demongraphic is very much nowhere near 2.5% - our actual number for IE users is 0.4%, for all versions of IE combined (just IE11 would be 0.2%). Even Samsung's browser ("Samsung has a browser?") drives four times as much traffic as all version of IE combined.
IE use has properly died down ever since Microsoft themselves started making sure folks weren't using it anymore. And they really don't want you to use internet explorer: Windows hasn't had IE set as default browser for years now. It comes bundled with Windows 10, sure, and IE11's EOL is contractually tied to the Windows 10 EOL, sure, but Microsoft is working damn hard to make sure you're on Edge instead.
If you have to support IE, because you have a target demographic that for whatever reason is forced into IE use, then sure: roll whatever code you need. But if you're developing for the current web landscape: no, IE is not your concern anymore.