Given no decent flexbox polyfills, I would doubt the existence of a good grid polyfill. If we can't do flexbox, how do we cope with grid?
Jen Simmons made a really good video about exactly this topic - https://www.youtube.com/watch?v=7msERxu7ivg
Rachel Andrews' blog post about IE and Grid - https://www.rachelandrew.co.uk/archives/2016/11/26/should-i-...
Mozilla article about progressive enhancement and Grid - https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Grid_La...
Some web developers out there are still supporting ActiveX components that no one is willing to replace. I don't think anyone would advocate building a new site using ActiveX though. At some point we have to move forward and adopt new technologies that improve the way things are built. We're at a point in web dev where Grid is ready for mainstream use.