The real question is: WHEN will Google have enough leverage to force carriers and device manufacturers to allow them direct access to upgrade the devices and without crapware or disabling features?
I bet one could jailbreak a device and flash a firmware hack to patch the hole if Google or another team released a fix.
Google lets manufacturers use their base OS for free given some restrictions, and yes, many of the devices use radically different hardware with different kernel modifications, GUIs, and drivers. It's a fragmented ecosystem, and it would be pointless to push updates without consulting the manufacturers on how such changes would affect such customized systems. Think of the many different Linux distros running various window managers, kernel versions, hardware, etc. You push the wrong update to the wrong distro and you break all sorts of things. Google doesn't want that liability. Not to mention, they don't have the authority to alter a device - it would void your warranty without the manufacturer's permission.
The smartphone market is less like the laptop market and more like the embedded OS market - highly customized software specifically for one configuration of a device and also tailored for the manufacturer's preferred interface and the carrier's preferred lock-in schemes with crapware and disabled features (so they can offer premium paid features).
Blame the carriers first, the manufacturers (who stopped thinking about supporting your phone about 5 months after they released it) second, and Google very last.
Look at Google's Nexus product line - those get updates first b/c Google negotiated to have a clean OS on good hardware that would be largely portable between carriers. It's not Google's fault people choose other less supported makes and models. If consumers only purchased Nexus devices, Google would have the clout of Apple and could command more authority on the design, implementation, and upgrades of Android devices.
It would be very nice if and when the Android market were more like the laptop market, but even then -- remember all those Windows XP machines that could upgrade to Windows 7, but the manufacturers never made drivers for the hardware? XP laptops upgraded to 7 sometimes didn't have trackpad drivers or webcam drivers... same thing could happen with android devices. Fix a kernel bug and suddenly your phone loses a feature because the manufacturer didn't bother to upgrade the driver for the new kernel.
The current arrangement is Google makes the software, Manufacturers customize it for the device and carrier. Google updates the software, Manufacturers support the device with software upgrades pushed over carrier networks. If google's made a patch or update (and Android 5 can work on older devices that couldn't take the 4.4 upgrade), then it is definitely the manufacturer's fault for not supporting their hardware and testing and rolling out the patch. If the arrangement is going to change to more like the Apple model - people need to start buying Nexus products and shunning all hardware that doesn't come with updates straight from Google.
I understand that the life cycle of phones is about 2 years, so It's hard for me to be upset about 2 year old unsupported hardware (Verizon has a "new every 2 plan"), but I certainly wouldn't blame Google for he issue when manufacturers and carriers are the ones blocking their ability to provide the updates. IF Google could update any old Android device on their own, they'd wipe out crapware and bloatware, enable the features Verizon and others have disabled by default, and get rid of crappy UIs some manufacturers put on their devices in favor of the Nexus interface.