My old PC, which my son now uses, is 7 years old and had a Ryzen 7 1700X (8 cores, 16 threads) in it which is 'unsupported' under Windows 11. This is a bit of a joke because I ran Windows 11 on it from the very first public beta (i'm part of the Windows Insider Program).
I upgraded the graphics card in my own PC to a RX 7800 XT last month and moved the RX 6700 XT which I had been using into my son's PC. The GFX card also required a PSU upgrade as it draws a fair bit more power than the GTX 1060 that was in there before. Whilst I was 'at it', I decided to put a new CPU in the PC as well. I picked up a Ryzen 5 5600 for £70 ($90) from AliExpress. The new CPU is only 6 cores, with 12 threads, but it's 2 generations newer, the cores are faster and more efficient, so overall performance is about 30% better than the old CPU, it also draws less power.
So my son now has a PC which is capable of playing modern games at 2K resolution and reasonable quality settings, which, FWIW, is fully supported by Windows 11. I think is a pretty solid upgrade for a 7 year old PC
Also, the RX 7800 XT, 650W PSU and Ryzen 5 5600 cost me less than £500 ($630), so i'm happy, he's happy and so is my wallet
Note: If you're going to swap CPUs on a 'modern' Windows PC, first check if you've encrypted your hard drive with Bitlocker and export the keys first. Modern CPUs include the TPM where the keys are held (known as Intel PTT or AMD fTPM), so if you swap the CPU, you loose the keys and the PC will not boot. This is not the end of the world, because you get a warning when the PC boots and are given the chance to put the old CPU (with it's TPM) back in the PC. You can then boot, export keys and import them when you have the new chip installed again.