The alternative would be to set watchlist to show all changes and not just the last one, but then it would show one row per change or a
group
of rows per page, and that would make it even more cluttered.
That never looked cluttered to me. :)
It did to me, and AFAIK, you and I started editing Wikimedia roughly at the same time (give or a take a year or two). A matter of taste, I guess.
When I show the Watchlist to new people, they interpret it in wildly different ways, all of which are incorrect.
Subpagination does help with this because you can filter new page
creations.
All the problems you mentioned I consider solved since about 2006 on it.wiki, modernise your practices.
Sorry, but I wouldn't call subpagination and namespace selection "modernised".
To begin with, to be able to use these things, one needs to learn what namespaces and subpages are; how many websites do you know that people need to *learn* how to use? I certainly don't want Wikipedia to be such a website. I want people to come here to write articles; this includes being able to participate in discussions about articles, and this shouldn't include the need to learn about namespaces and subpages.
Also, why do I need to modernize my practices *separately* from other projects? I can understand that articles need to be written in each language (and I'm developing software to make that easier), I understand that the human side of community practices needs to develop on each project separately?
Most projects in most languages - that's many hundreds of projects - don't have admins and techies that can manually customize templates, namespaces, bots, RSS, and so on. It doesn't scale.
Flow basically productizes[1] these practices, makes them common, and removes the need to *learn* stuff. No, it's not ready yet, but the direction is right.
[1] I'll keep repeating that I hate the word "productize", but I love the idea behind it.