This is why for the first time since I started owning smartphones (2010), I am going to switch to iPhone.
Sure, one could install an updated and more secure rom (assuming it exists for your device). But, the vast majority of users don't care or won't bother to go through that process, rendering it a completely ineffective solution for the general consumer market.
That happens to be true now because Apple has dropped support for many iPad models with iOS 10, accounting for up to a third of all iPads in use.
Running iOS 9 on the iPad 2, 3, and iPad mini was frustrating. This was only three months ago, so I wouldn't rule it out for the future yet.