In who's opinion is there an "absence of trouble shooting steps"?
Restoring a device having this issue and setting up as new would be where I would start. Sync the photo library in question using iTunes to start and see if there are local storage issues/discrepancies. Keep iCloud of of this.
The I would add photos in batches of several hundred and sync using iCloud. See if the issue manifests itself at some point that can be isolated. Now that iCloud is in the mix, does the issue show up?
I am a wedding photographer and routinely show galleries and slideshows on my iPad 2 that are placed there using iCloud. I show them while offline, online, it doesn't really matter.
iCloud Drive to IOS devices seems to be what most users want... on demand/usage based download.
Your common thread comment gets me. You are blaming Apple solely for a situation created by all tech companies and consumers alike. In no way did Apple create a demand for always-on content.
It is laughable for you to isolate Apple for "designing products that depend on it, building in dysfunctionality" and then to add a comment on an error message that is about a local storage issue, by saying "which we see in this erroneous iPad error message as well as in other products."
Streaming music over the internet is something that has been driven by all levels of the economy. The consumer and the provider. Spotify, Pandora, Tidal and yes, Apple Music.
We've had streaming live wirelessly since Marconi started it at the turn of the century. The 20th century.
We called it radio. Music streaming, as we know it now, is an innovation that could have been easily been done with "radio-on-demand" were it technically feasible. In the 50s when a teenager called a radio station to ask for a song to be played, they were streaming music. Same with the TV industry's fascination with apps. We've broadcast TV signals for years, but on the TV station's agenda. Now apps do it on demand. How did Apple create all of this?
If you feel the need to point fingers... what about Google? Name me relevant 5 things you can "do" with Google that don't require connectivity? Facebook? Uber? Open Table? Yelp?
"I'm told in the US too."
"as well as in other products."
"no troubleshooting steps I have found"
These don't sound like actual observations to me. They sound like someone venting about spotty data service in their country. Which is your right. But please... context. Be angry at the correct players.
EVERY TECHNOLOGY company has begun to "assume universal fast internet access for these products when the reality is this years off..." Google, Microsoft, Apple, Facebook. LinkedIN, CNN, MLB.com, ABC, CBS, NBC, BBC, CBC, Dropbox, Backblaze, Amazon, Netflix, NFL.com.