But "ease" isn't the problem - the issues OEMs have are because they literally go hack and fork the AOSP source itself (making upstream merges hard or impossible) for sometimes really dumb reasons. This is also the source of constant headaches for us app developers (like the recent case where Realm found out that Samsung broke memmove() on their devices!).
The other issue is that there's zero (0, no) incentive to update the devices. No matter how easy it is - the OEMs see that as a pure cost that won't be recuperated. For each of the (literaly!) 100 devices they churn out per year they need to get new drivers from the SoC manufaturer (and Qualcomm pretty much does not give a crap about SoCs of the previous year, especially lower end ones - which makes this process stop there), update the kernel and move all their specific hacks to it.
I don't see how these changes Google did will change incentives. The only way we might see a change in this field is by a few class action suites from users being left without updates or regulators putting down the punitive damages hammer. Everything else is just Google kindly hoping OEMs will stop being dicks from the goodness of their heart.
In car industry we have strong regulation which demands that your car is serviceable at least 5 years since last unit was sold (and that their security issues are fixed by recalls). We need that for arguably the most important electronic devices in our lives as well.
