At least on IOS you're stuck with safari/the system webview, so even if you make a web browser app (this includes chrome/firefox) they're using the safari engin

At least on IOS you're stuck with safari/the system webview, so even if you make a web browser app (this includes chrome/firefox) they're using the safari engine. The issue stems from the slow adoption of certain technologies. That was the issue everyone had with IE 6 - everyone used it but it lacked modern features so it sucked to use, but you had to because of it's market share.