The Gemini protocol throws away a huge number of advances - in effect throwing the baby out with the bath water.
Gemini protocol could have been a subset of HTTP and the document format could have been a subset of HTML. For instance, if you decide to not implement cookies, javascript etc but if you retain the ability to have formatting for texts, tables, images etc it would have been sufficient.
And even in the case of images, the protocol could have mandated that images cannot be accessed cross-site. The same restrictions could have been placed on other aspects such as the style sheets.