Flutter web is working much better for me in the last couple of months. I did everything in flutter without trying to import any third party js libraries. My guess is that is where a lot of your trouble is and in trying to add in iframes. When I used 100% flutter libraries that were compatible with web it works great for me. But yes it's still beta so it's not as good as react on web yet. Plus I use it for web apps not regular websites.