Even Microsoft considers IE dead and buried, so your expectations that eBay support it are are unrealistic.
(I'm a steadfast user of really old Firefox versions and understand the consequences of doing so - it's often my fault when something doesn't work because I'm using one of the old versions. Using FF31 to post this and do much of my eBay business in FF3.6.24)
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While Windows 10 uses the newer, faster, much more standards compliant Edge browser as its default, it still ships with Internet Explorer 11. Enterprise customers with legacy systems from time to time want to make Internet Explorer 11 the default, but Microsoft doesn't think this is a good idea. Internet Explorer 11 isn't being updated to support new Web technology (and indeed, hasn't been updated for many years), existing only as a compatibility tool to access legacy "designed for Internet Explorer" content that simply won't work properly in any other browser.
As such, while it might be tempting to set Internet Explorer as the default to ensure that any intranet and line-of-business applications continue to work, that comes at a price. It will be slower, less secure, and increasingly incompatible with the broader Web as developers drop the old browser from their testing. So please, use it only when it's absolutely necessary.
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IE desktop market share is approx 5%. Chrome is over 50% - if eBay breaks something in Chrome, you can legitimately get on their case 
