iOS shows this even more. My 3gs was reasonably fast on ios4, slow on ios5 and like a dog on ios6.
Agreed, but iOS isn't exactly the same thing. The rate of IPC gains in mobile processors has been at a pace not seen in x86 land in
many a year. Comparing your 3GS's 600 MHz ARM Cortex-A8 CPU to the Apple A6 Swift cores is like comparing a Pentium Pro to a Core 2 Duo. They were doubling and doubling and doubling (and tripling in some spots) performance year after year. Plus, RAM sizes ballooned too (the biggest issue with the 3GS on iOS 6 was the RAM limits on the old device). I'd also say they've gotten better at that with iOS since the 3GS on iOS 6 days. It was touch and go for a while at first, but iOS 8 works just fine on my old iPhone 5. My mother-in-law has it, and still uses it, and it is fine. My iPad 3 is... Less fine. But that was a compromised device from day one (the GPU was really just
barely fast enough to run that display), and the iPad 4 we have at work is much better with it.
But, I think including every machine they've released since 2009 (and including more powerful machines back to machines in 2007) is pretty decent for a free update. It is 2015. XP was supported for absurdly long, but Microsoft isn't patching Windows 8.0 anymore either (because 8.1 is a free update to everyone who can run Windows 8.0).
Does it compare to long-term release and support cycles for enterprise OSes? No, but that's not what it is for, it is a consumer OS. And in my experience in practice, Yosemite runs as-well-as-if-not-better-than Mountain Lion on machines that support it, much like Windows 8.1 does compared to 8.0. Up until 10.10.3, I'd have been a bit more skeptical and stuck with Mavericks for best stability, but I've been quite happy with it since the most recent huge bugfix release.
If your machine is newer than mid 2009 or so, and probably even older, then you can upgrade for free if you want to.
Like I said, I do not dispute in any way that they
do drop hardware quicker than Microsoft. They do, but I think it is overall healthier for the platform to drop them when they do. And in many ways, it is often healthier for the customer's machine too (rather than squeezing it to run on something it can't, like iOS 6 on a 3GS). But, in this particular instance, I can see their point. And they haven't been very aggressive in dropping older Mac hardware
since the big 32-bit/64-bit schism between 10.6.8 and 10.7.
It does stink if you have a Core 2 machine that can't get past 10.6.8 or 10.7, I grant you. That machine is going to be a pretty darn old computer, though. I'm sure there are some that are still in service out there (my mother-in-law has an old one which she handed-down to my father-in-law last Christmas when she got her new 13" Retina), but... It is pretty old, and cruddy, and only still worth using at all because of the SSD I put in it.
There's
certainly still room for criticism in the iOS space (they're still selling iPad 2 hardware right now in the iPad Mini 1 shell, which is crazy-pants). But on OSX their track record here is decent and understandable, if not ideal. If you assume that they weren't going to go back and fix Lion (and they didn't for FREAK or other recent vulnerabilities where they did patch 10.8, 10.9, and 10.10), and every single machine that can run 10.8 can also run 10.10 for free? Dunno. I think that's acceptable. It is a patch, with a bunch of new features. How different is that from Windows XP SP3?