Indeed, tables are an essential a thing which should be there, but it should be implemented in a way which makes it impossible to abuse it for layout, it should only be used to represent actual tables. I would even add column data types so the browser would be able to let the user sort them in a meaningful way (e.g. I hate Wikipedia tables which have sorting but can only be sorted alphabetically or something like that).
As for multi-column layout - it's a work for the browser to do on the user demand. View should be decoupled from the content.
For cases when you want to control every aspect of how is the information displayed there is HTML.
Things like Gemini should not have formatting features besides those semantic which MarkDown has.
Even better. Gemini supports alternative content types, so there's nothing to prevent you from serving up Markdown documents in response to a Gemini request. Worst case, your client will display it as plaintext (which will be still very readable), or in the best case, it will kindly render it into something pretty but still simple.
The fact that tables must be sorted with JavaScript is a fundamental flaw in the HTML specification. Sortable tables that the website cannot ask to be unsortable are a strong disincentive to use those tables for layout. Mandatory thick & ugly borders would also help.
As for multi-column layout - it's a work for the browser to do on the user demand. View should be decoupled from the content.
For cases when you want to control every aspect of how is the information displayed there is HTML.
Things like Gemini should not have formatting features besides those semantic which MarkDown has.