Microsoft Edge: Vintage Web Tech

I went to one of the sites and I saw this Vinage Warning sign on Microsoft Edge.

This is new to me as I never heard about the vintage web tech.

What this basically means that some websites runs on very old browser and Internet Explorer.

I found a link on how to resolve and troubleshoot the Vintage Browser:Microsoft Edge: How can I remove 'You've stumbled upon some vintage web tech. Open with Internet Explorer' message from showing?