I keep seeing Astra make beautiful 3d stuff online, yet when I feed it some old school RuneScape assets (even tried with some very detailed guidelines) and asked it to generate some new plausible assets it failed horribly.

I think there’s still something really off with current (frontier) models when it comes to creating “novel” stuff? Even 2004 style graphics..

Or am promoting it wrong?

It's funny seeing this when I was going to mention runebench

https://maxbittker.github.io/runebench/

Did you try blender MCP and prompt for low-poly vertex colored assets?