Android users update slowly because Android updates depend on the OEMs, and the OEMs update slowly or not at all.
With iOS, Apple releases an update, and then everyone with an iOS device made in the past N years (where N is 4 or so at the moment) can download it more or less immediately.
With Android, Google releases an update. Then the OEMs slowly start working on updates for their various devices. If they feel like it. Often they just don't bother. Then if you're lucky your OEM finally gets their job done and you can update. And by the time that happens, you're lucky if it's only one or two point releases behind what's now the latest.
And for phones distributed through carriers, once the OEM provides an update, it then (probably) gets tested by the carrier, and only then (eventually) pushed out. Sometimes the carriers don't even distribute updates the OEMs provide.
With iOS, Apple releases an update, and then everyone with an iOS device made in the past N years (where N is 4 or so at the moment) can download it more or less immediately.
With Android, Google releases an update. Then the OEMs slowly start working on updates for their various devices. If they feel like it. Often they just don't bother. Then if you're lucky your OEM finally gets their job done and you can update. And by the time that happens, you're lucky if it's only one or two point releases behind what's now the latest.