From few weeks I replaced my I7 3770K OC 4,4Ghz (from 2012) by an I7 10700K at stock clock for now and I don’t see the “Limited by mainframe” anymore (or very rarely) and my cpu usage still have lot of headroom before reaching 100%. Coupled with my “aged” GTX1080 Oc 10% and the sim run perfect at 1080p 60Hz with mainly Ultra settings (I limit my fps at 60 in Nvidia control panel). Before I thought I could compete with modern core with my OC at 4,4 Ghz, pffiiuuu. At similar frequency (locked for testing purpose), the 10700K atomize the 3770K.
You’ll be more than good with a Intel I9, even if I think Ryzen family is more interesting now.