However, your statement that every single SSD you own has failed does not match my experience at all.
I've two failed SSDs (they aren't long enough on the market yet to have more data about when they usually fail).
One is an external SSD where the controller broke beyond repair after 2 years. It would be easy to continue to use this SSD just connected to a new controller. But someone, who probably thinks like you, decided to solder and glue everything together, so it wasn't possible to get the SSD out of the case without breaking the SSD. What were the benefits of soldered and glued external SSDs again? Never mind, I learned my lesson and I only buy cases with controllers separately from the SSDs wherever possible.
The second SSD reached end of life. It's my first SSD, 120 GB. The number of writable sectors goes down quickly. However, it's still fine for reading, so I connected it to our old Wii to just load a bunch of games from it. If it was a new MacMini the whole computer would be dead.
And whatever you may want to say, there is no reason at all to prevent replacement. You highly underestimate the skills of the Apple engineers if you think that's required for space or whatever. And it's out of question that the ability to replace an SSD makes the whole machine MORE reliable in the long term and not less reliable.
But yes, upgrading SSDs was a big point as well. Especially in the beginning when the capacity of SSDs grew quickly every year. Who would want a computer with a non-replaceable 64GB SSD today from just a couple of years ago?
Yup, I find I need them pretty often. However, again it is a question of tradeoffs. I pay a few hundred dollars a year for each of my offsite backup options and they are completely automated. Were it to cost me hundreds of dollars a month or take many hours of my time, I might make different choices about what I saved.
So if you had to pay 10 times the price for the storage, would you say it would be a good tradeoff if you had to pay twice the price for the computer as well for this?
I could think of a lot of reasons why Apple might say, we block every other backup storage service and you MUST buy our cloud storage if you want to make backups. It's just so much more reliable if Apple does it, and the connection can be much more secure, because security could be done in hardware or whatever.
I have lots of old machines that I fire up on occasion from an 1978 MITS Altair 8800b to an original IBM PC, an XT, an AT, a Mac, a Mac SE, many NeXT Systems (from 1988 through 1997), HP PA RISC systems (running OpenSTEP), and probably still have a PDP-11 that works. However, I have nothing in production that is older than 6 or 7 years (I would have to check).
I don't have the space to keep all old PCs. I mostly give them away to neighbor kids. Which doesn't mean I'm fine when they break some months later.
You have said how old your oldest Mac is, but I am much more interested in how old your newest system is. I am also still interested in what you do/for what you use your Macs.
My lastest Mac is just a 2014 MacMini. I stopped buying Mac hardware after that because Apple doesn't have any hardware which fits my needs.
I need a fast graphics card for Autodesk Maya.
I need lots of memory and disk space for database analytics and for producing music.
I need a fast CPU for pretty much everything.
What I DON'T and will NEVER need is a monitor. I have a great ultra widescreen monitor and will never go back. Buying an iMac just to put this thing under the desk would be ridiculous.
I can get this and even more than I need as DIY for $1700 or for $13000 from Apple for the exact same experience. I love macOS and I hate Windows with passion. But even I have limits. I would buy some sort of (mini) tower from Apple in a blink of an eye - but not for the price of a new car.