It's not about tapping an icon, it's about the understanding that turning things off has non-obvious consequences on other bits of features, an understanding that can only be reached by getting down technical rabbit holes.

e.g (just one example) turning WiFi completely off degrades the ability to geofence, one's automations may be delayed or non-functional and one would be bewildered as to why. Turning WiFi off one day, forgetting about it, then having apparently unrelated things not work the next day is hard to diagnose.

There's a next-day trigger for sure for the WiFi disconnect+no-auto-reconnect ("disable WiFi" in the support page†) but I must admit that I don't know what's the exact trigger - if any - for the master WiFi switch in Settings.app ("turn WiFi off" in the support page†) to be turned back on. Next day? After a software update (e.g an automated nightly one)? Exiting hotspot mode? As you suggested, a bug? Nothing and it's people forgetting they have turned it back on "temporarily"? The support page† doesn't say anything about it.

Should one desire to enforce WiFi off as a policy, the shortcut can act as a safety net around all these cases, the tool is available to help automatically enforce the policy, and I don't think it's helpful to sit and hold one's breath til one turns blue because it shouldn't do what it's doing, refusing the opportunity to get control back.

I agree that Shortcuts is awfully limited, sometimes inexplicably so. I mean, picking up a random wallpaper from a Photo album every X hours should be entirely doable, yet there's just no way to do it.

† https://support.apple.com/en-us/102412

EDIT: I have tried the hotspot thing.

    - set iOS WiFi off
    - request hotspot connection from another device
    - iOS WiFi turns on
    - if no known AP is in range
      - iOS WiFi turns on
      - hotspot connection succeeds
      - upon hotspot disconnect iOS WiFI stays on (BUG #1: should restore WiFi off)
    - if a known AP is in range
      - iOS WiFi turns on
      - iOS WiFi connects to AP (BUG #2.a: should not connect to AP)
      - hotspot connection fails (BUG #2.b: caused by #2.a?)
      - WiFi stays on, connected to AP (NOT BUG: consequence of #2.a)
      - (optional) re-request hotspot connection
        - iOS WiFi disconnects from AP
        - hotspot connection succeeds
        - upon hotspot disconnect iOS WiFI stays on (NOT BUG: consequence of #2.a, which caused WiFi state == on at second hotspot-request-time)
        - iOS WiFi eventually joins AP

This may happen unattended if the requesting device has "auto-join hotspot" enabled.