My CPU is about 8 years old. i7 4790 (not even the K version). 4th gen. I was a bit disappointed with the lack of performance boost, when I upgraded my video card to a 6900XT. In a stroke of luck (because they pretty much never sell components at the NEX), I ran into a stack of 4090 Founder's Editions on the shelf, at retail (and with no taxes), so I picked one up... only to find out that it was only marginally better.
Turns out that my ENTIRE SYSTEM is bottlenecking video card performance. From PCIe bandwidth, to Memory, to CPU. So, I for one, am jumping on the 7950x3d as soon as I can get my hands on one. Price be damned. Already have an x670E-PLUS TUF Gaming motherboard, 32GB of DDR5 6000 RAM, and of course, the RTX 4090. And an M.2 drive rated at 7200MB/s that people complain about benching closer to 6000MB/s... but my current SSD is more like 520MB/s, so I'm pretty sure I'll be pleased.