Yeah, the decision was made a while back to start dropping support for IE 11, as our usage numbers for it had dropped below 1%.
I think for most people, it's very much possible to continue supporting it. The conditional loading of polyfills is a solved problem, and we've even got it a bit more streamlined than before in the upcoming V2 of our theme components.
The biggest barrier to us supporting IE11 has been the lack of Grid Layout support. For better or for worse, the new version of our header that's being rolled out soon uses a lot of grid, and since Edge shipped grid a few versions back, the Powers That Be decided that it was time to truly break IE compatibility.
Personally, I'd like to keep maintaining some form of compatibility, even if it's just in our fallback stylesheets. Producing an ES5 bundle wasn't hard, deciding which bundle to load wasn't hard (especially since ES modules shipped everywhere but IE), but it was decided that it wasn't worth it for the small number of IE11 users we were seeing.
Our IE experience is probably atypical for most businesses. Being a university, we have three main audiences: students and prospective students, faculty and staff, and alumni. Each group is different, but for the most part, they're either using mobile devices or recent laptops running Chrome, Safari, or Edge to access our sites. The biggest group is our students, and we tend to see a 4-5 year long cycle with them. That's about how long it takes a big release, like Windows 10, to reach near-100% adoption in our student body. This is because our students tend to buy a new laptop right before their freshman year and keep it until they graduate. Our faculty and staff are mostly on a two or three year hardware refresh cycle, so they're usually running a recent OS too. So, at this point, the majority of our users are using a device that has never had IE11 as the default browser.
Like I said, I still think it wouldn't be terribly hard to keep supporting IE, but even though I did a lot of the initial work, I'm no longer involved in any of the decision-making in this area, so my opinion doesn't count for much.
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