"It's instantly clear to other users what stuff is built up by the tree owner, and what is subscribed. There are benefits from subscribing, as you get continued updates to parts of the tree with no work required."
I'm not sure about the point you're trying to make with this statement. Benefits from subscribing as we get continued update to parts of our trees with NO work required? Whatever. Just because Ancestry presents so-called "hints" to subscribers according to the information we add to our tree doesn't mean those "hints" are in the least bit accurate (mostly not) OR that we would even add the purported "hints" to our trees.
You mention that there's a "generational" gap in regards to technology capabilities and older family historians. I consider myself to be pretty up to date as far as technology in regards to family history.(I'm 47, BTW, and have been doing family history since I was 11.) I realize the positives of "crowd-sourcing" as well. In theory, it sounds all good. In practice, I'm not so sure. I'd be up for trying out a "crowd-sourced" tree. I'm just not going to allow my own work be a guinea pig for such a tree because my private tree includes many other family lines than my own.
I've worked very hard on my family history for a lot of years and, still, am only back to the early to mid-1800s in most lines of my direct family. Only a few lines, (maybe 2), have I been able to document to the 1700s after 30+ years of research, which I think is a usual occurrence unless a person 1) has money to travel extensively (plus pay for copies of the records found) AND/OR 2) has money to pay for someone else to do research for them (as shown on TV).
I don't know anything about you or your experience in family history so I can't say whether you understand the point of view of those of us who've been working on our histories for a long (LONG) time or not. I think most of us are willing to give new tools and technology a try but am afraid of losing all the work we've done for years.