Not at all. Most platforms are slow to add new features, and even slower to remove them. This is why we can still play videogames from 10+ years ago on modern Windows systems.
Has this held Windows back? Yes, a bit. But I for one appreciate that I don't have to buy all new software every year for it.
And even in cases where compatibility is broken, there's still the possibility on Windows or GNU/Linux or even OS X to fire up something along the lines of DOSBox or VirtualBox or somesuch and be able to recreate the necessary environment to play 15, 20, even 30-year-old games. Last I checked (which was admittedly a long time ago, seeing as my ship-jump from iOS to Android was a few years ago), you have to jailbreak an iOS device in order to achieve similar functionality thanks to Apple's rather-draconian restrictions on such things.
Apple's attitude toward iOS - move fast and break things - is in stark contrast to even OS X, where a lot of software made for OS X versions as old as 10.5 will still run relatively happily (though apparently Yosemite broke quite a few things).
That said, there's a time and a place. On my servers, for example (which are typically running OpenBSD or some GNU/Linux distro), I'm at least somewhat-okay with backwards-compatibility breaking (within reason) if it means having better performance or security. In that context, I'm relying far less on closed-source software (if I'm using closed-source software at all, which is incredibly rare for me when it comes to servers), which means that most of the software I actually rely on will at the very least usually have community-supported patches up the wazoo to support those backwards-compatibility-breaking changes (like OpenBSD's switch to a 64-bit time_t, which basically just amounted to recompiling a bunch of stuff - most of which was already done by the ports tree maintainers when creating binary packages).
Has this held Windows back? Yes, a bit. But I for one appreciate that I don't have to buy all new software every year for it.