The mobile phone cycle is just a redux of what happened with PCs until around 2007. Computers were getting a lot faster and software coming out actually demanded better computers.
Honestly, around 2009 and the introduction of the Core 2 Duo, computers became good enough for most people.
I just retired a circa 2009 Core 2 Duo 2.66Ghz Dell laptop with 8GB of RAM running Windows 10 with one of the last great 15 inch 1920x1200 displays (as opposed to the 1920x1080) as my Plex Server about two months ago.
In day to day use, I couldn’t tell the difference between that and newer computers besides the spinning hard drive vs SSD. It has a gigabit Ethernet port and was wired into my network. It had just as much of RAM as most computers sold today, the hard drive was the same size (but much slower), the screen was better than what comes in many consumer laptops and most computers today don’t come with gigabit Ethernet.
In 2009, a computer from 2000 would have been unusable. (http://www.topdesignmag.com/top-performance-computer-looked-...)
Mobile processors are now getting that way. While an iPhone 5S from 2013 is perfectly usable running iOS 13, there is no way that an iPhone 3G from 2008 would have been something you wanted to use in 2013.