I disagree for the reasons stated. Apple can have a big enough market to justify doing something but still not do it.
As I said, they will not give users a totally self-upgradeable system, it is built into the Apple DNA that profit comes before what the customer really wants. You don't make Apple profit by encouraging customers not to be forced into returning within a max x year period. Something that would be lost with a PC style system.
The proof of that is everywhere for everyone to see.
Upgradeable Ram in the 2018 Mini was seen as a win, I saw it as throwing the dog a cheap bone. Yes, it is upgradeable, user upgradeable? Not so much, given the tools and surgery required it's not for everyone. Even fairly competent users on MR have reported breaking connectors in the process of upgrading.
A niche opportunity, compared to how you would upgrade Ram in everything else that is not a Mac where thought was given to make it as simple for everyone as possible.
It will take a bit of time but when faults start emerging on Mini's and they head down to the Genius Bar to get it looked at we all know what is coming. 'You replaced the ram yourself? Yeah, that's what caused the issue, no warranty cover, that will be $xxx to fix please.'
I am not bitter about it all, Apple, the Mini and macOS serve a purpose for me and it all works well. If my new mini lasts me five years I will be over the moon. If I fall out with them I like Windows 10 a lot more than previous versions and could get by.