I have a couple Mid-2010 2.4Ghz White MacBooks and 13" Pros, and they are all completely usable (if not a little warm) for the modern web. Can't say the same for my 1.67Ghz PPC collection from only 7 years prior.
I remember even circa 2013/2014 a PowerMac G5 1.8 struggled browsing the web smoothly - we had one in high school running 10.5.8 (which I had clandestinely upgraded from 10.4) and QuarkXpress. Got to be painful at times.
Conversely even my 2008 White MacBook browses the web decently well (and there, the main limitation is the Mac OS version its capable of running).
My relatives are still using a Late ’09 C2D iMac for basic home office functions, though it is beginning to show its age...