Everything is slower across every single facet of computing. Something is happening. I have a brand new Mac Studio M4 Max with 64gb of ram and every site is still slower than it was on a 2011 Mac Book Pro.
Web developers should be forced to use hardware that's roughly at the 10th percentile in performance of their user base, not the 90th. Alternatively, make performance a WCAG concern.
Chrome Dev tools, and hopefully others, have a performance monitor option that lets you throttle the CPU and throttle the network. It should be plenty possible to test performance of sites on simulated 10th percentile systems, but this just seems low priority.