To be fair to apple, people keep their macbooks for years and years, keeping them out of landfill longer. They are well made and the design doesn't really age. Written on my 2015 Macbook pro.
A typical "Upgradable" PC is in a box 10 times the size of the mini. If you upgrade the GPU on a PC, you toss out an older GPU because it has pretty much zero resale value. Typical Apple hardware is used for 10-15 years, often passing between multiple owners.
This is particularly true on the lower end where a 10 year old part is even interesting.
Like the Ship of Theseus thought experiment, at what point does a thing no longer have sufficient continuity to its past to be called the same thing? [1]
Regardless, I have a hard time believing a 20 year old computer is "working like a champ". I've found the most people who say their <insert really old phone or computer> works perfectly have just gotten used to the slowness. Once they upgrade and try to go back for a day, they realize how wrong they were. Like how a 4k monitor looks "pretty good" to someone that uses a 1080p monitor everyday, but a 1080p monitor looks like "absolute unusable garbage" to someone who uses a 4k monitor everyday.