I have no issue with a 'web-only" option, as long as it does not compromise current or future email group functionality, but I doubt that I would use it. I like groups.io because it manages an email group well. There are web platforms, like Wordpress, for web sites with options, such as formatting, that I would not expect from groups.io with its email orientation. If a web-only option usurped development and support resources that could be devoted to improving groups.io as an email group platform, I would not  be happy. On the other hand, if web-only is easy and maintenance free, I'm okay, but in my experience, bolting wings on a lawn mower makes a flying lawn mower, not a jet plane; when you need a 747, go to Boeing, not Lawn-Boy.