Is anyone aware of other visual programming paradigms which are not based on (or reduce to) the blocks&arrows model?

I cannot say I was ever satisfied in in every context where I saw this model applied. My experience ranges from trivial languages such as this, to compositing software, DAWs or something more sophisticated such as programming-oriented signal generators (where blocks are often used as filters/generators and edges as I/O connectors), to workflow editors...

It "might" look intuitive at first[1], but the network just becomes unreadable as soon as you have more than 10 nodes or non-linear behavior (with edges eventually crossing). Auto-layout just becomes a major problem to be solved. Auto-layout also destroys the visual locality of your program, so it actually goes against the programmer for anything non-trivial. Manual layout is something I do not want to take care of either.

Is any experiment or research being done that goes in a _different_ direction?

[1] I would actually say "less scary". I'm not convinced a simple programming language in the spirit of "BASIC" is less difficult to comprehend in the technical sense.

Circuit-based skins work well in the right context. Do a Google Image search for "unreal blueprints" to see many examples of them in use. Blueprints visual scripting probably powers the high-level logic in a video game you or someone you know has enjoyed.

The other popular approach is fill-in-the-blanks, a visualization that looks more like a tree than a graph. The first good version of this I saw was the Warcraft 3 scripting system. It inspired the visual scripting system we built for Tribes, SWAT, and the first Bioshock back in the day.

You can also follow Eve for some modern experiments along these lines: https://github.com/witheve/Eve