You may be surprise to know who is Heydon who co-author in the article. https://inclusive-components.design/ https://inclusive-components.design/ IE11 is mean

You may be surprise to know who is Heydon who co-author in the article. https://inclusive-components.design/ https://inclusive-components.design/ IE11 is meant for supporting legacy sites and Microsoft doesn’t recommend consumers to use it. It make sense to work on Grid and Flexbox for new sites.