EDIT: assuming here that "just make the page simple" is not an option. If the page layout is advanced enough that lacking CSS is a serious instance, you'll need two versions (or a version and an "export") anyway.
An option that I strongly don't recommend but it is doable, is to make the page with tables, then format the tables with display:flex or display:grid and the adequate related properties for the "modernized" view for browsers that support CSS.
Then again, nothing really prevents you from doing things the better way: making two pages and linking from one to the ther with a link like
It's even easier to maintain, in particular if you have a good workflow / build system for composing either page from the data you want to show.