Apple has terrible update policy. Microsoft still supports Windows XP which is 12 years old and widely used out there. Apple should learn something from that, allow customers to downgrade to every compatible OS and provide security and bugfixes to every OS they made in last 20 years. That would be customer care.
Microsoft still supports* Windows XP because their replacement OS (Vista) was 7 *years* late being released, and had serious enough issues that Microsoft's primary customers (corporations) avoided it like the plague. Had XP support ended on Microsoft's normal timeline, it would have been unsupported several years before Vista was even released.
* In reality, Windows XP support ended about a year and a half ago (April 8th, 2014).[1]
[1] https://www.microsoft.com/en-us/WindowsForBusiness/end-of-xp-support
Bottom line: I wouldn't recommend buying Apple product to anyone who wants to make a long-term investment. And I would advice against upgrading OS to the next version, because it'll render device less usable than it was before the update.
Apple has the longest hardware support of any vendor in the smartphone market. Who would you suggest instead?
(Google's Nexus line of Android phones are the only ones that come *close* to support duration.)