I don't think anything is more than "pretty much" plug and play. if you buy the "Desktop kit" you connect the display and mouse, stick the SD card provided into the slot, tplug in the power and it boots to desktop with a half-decent application suite. Apart from the familiarity & processing power, I don't see the big difference.And that's my point "pretty much plug and play" is different than plug and play.
Not as much as having a fixed internal storage device with 256GB+ of storage.Easily rewritten also translate to loss of important files, family photos etc.
Alternative: give the kids (or kidults) their own SD cards to corrupt - takes seconds to swap.
I was really speculating on why they left out the M.2. drive option from the Pi 5 - the Pi 5 SoC does support "proper" NVMe drives (not via a USB3 bridge like the earlier Pis) Running off a SD card is definitely the deal-breaker for me with the Pi 500 - although I'm seriously considering building a Pi 5 or CM5 system for fun.
You can put together your own "Mini like" system with a regular Pi, Pi-branded keyboard and mouse, metal case w/cooling and 256GB M.2 NVME for about £170, so - if it were on their agenda I guess they could have done a Pi 500 with 256GB SSD for the £150 mark. It was obviously considered because all the markings for a M.2 slot are there on the logic board of the 500.Sure, but at that price point you are competing with cheap Windows systems run out of the box and are familiar to users.
It would be interesting to see what happens now they've split the commercial arm from the charitable foundation. With the Pi 5 they're kinda at the point where they've got the basis for a viable a mini-PC ready to "fork" from the hobbyist/maker boards.
Personally, I use Pi 4s to muck around with Linux based things, like media servers - which would also be the main reason that I might consider an A18 Mac Mini, were such a thing to exist (or, otherwise, a refurb M1/M2 Mini). However, I've just added a 2TB M.2 SSD to my Pi 4 media server - £100 for the stick, £20 or so for the M.2. case extension - which is where the Mac Mini route fails dismally.