The iPhone and iPad are fine platforms; I use them regularly for my work. However, they are a far cry from Alan Kay's Dynabook idea. A better base for developing on the Dynabook idea would be the Microsoft Surface line of tablets, which can run the full versions of Windows 10 Home or Pro and thus can run modern Smalltalk implementations such as Squeak or Pharo.
I wish there were more work done in the area of composable GUIs, where the core logic of applications is scriptable and where these elements can be combined in ways that could be even more expressive than Unix pipes are. Every now and then I have thoughts about taking a modern Smalltalk implementation and writing a suite of composable GUI apps as a demonstration of this idea.
This topic always takes me back to a Hacker News comment I read many years ago (https://news.ycombinator.com/item?id=13573373) about composable software versus monolithic applications and how commercial software companies are predisposed to support the latter while the free software movement should have focused on the former. I still don't think it's too late, however, as long as there are some vendors selling hardware that users can install their own software on without needing to use a certified app store.
There is a related issue at play here when it comes to how systems are developed. It takes an enormous amount of sustained effort and time to create whole computing systems (hardware, OS, design, etc). The FOSS movement is not really capable by definition of doing this, since it is dispersed and not funded at the level that today's major platforms have been funded. This is precisely why FOSS is so Unix-centric: that is the predominant and free OS that was available at the time the whole movement really came about.
It would take a years-long, well funded research effort to build a truly new computing environment. On the technical side, the desire and some of the knowledge is there. We simply lack funders that are willing to pony up a good amount to the right people and leave them alone. That is was ARPA, PARC, and Bell Labs were able to do in their time, and the disappearance of this kind of funding environment is exactly why we are still reiterating on the accomplishments of those institutions today.
Where the browser is the platform, you might consider using custom elements to fill this role: https://html.spec.whatwg.org/multipage/custom-elements.html#...
The OSes were removing friction and making it easier and easier to craft our own solutions from tools in an expanding and interoperating toolbox.
And then we got iOS and iPad and each app has its private data, no more command line, no more generic project folders, no file system access, not even copy and paste, and years of "well, I guess you could email it to yourself" or "just pay us every month for iCloud instead of plugging in a thumb drive" nonsense. Those restrictions are being partly and awkwardly eased somewhat, but we're being assured that having self-contained, pre-designed apps for everything is the new way. Apple (which seldom makes claims about the future) is telling us explicitly that the iPad is what the future of computing is going to be. That is not appealing to me, nor is it intended to be.
While it is true of course that you can do "real work" if "there is an app for that", you can't even write your own app for that without paying Apple a yearly fee and getting their approval to put it in the app store. I hope this won't be the only future of computing.