It only makes sense for niche use cases, like your grandpa who is happy to have a single spot in his home for the computer, or a reception desk at a business, etc.
If you need to push performance you'd probably go for a Mac Studio, no? Or at least a Mini.
This is basically 99% of the proposition of the iMac at this point. If you don't need the specific all-in-one, color, and other design aspects of the iMac or can afford a Studio display, there's no reason not to buy some other display + a Mac mini or a laptop + display
If you need portability, you have your phone already.
I did have a 2010 Mac mini server, don't remember how it compared to the non-server one other than having dual HDDs instead of the DVD drive. I put them in RAID-1.
Though I have had good results buying 1-2 generation old refurbished Macs as my secondary machines or for family members who don’t need cutting edge everything.
It’s even more valuable now that Apple silicon of every generation is more than enough to run every non-power user use case short of newer video games.