I looked at this video and several others by Bret Victor. The examples he gives are interesting, but I don't think that they scale.

I think that the most important thing is interactivity, whether one is manipulating graphics or writing code snippets. Fro the most part, I think it would be faster to build up a graphic or an analysis by building up Wolfram Language code than to do all the (similar in principle) steps needed to make a graph directly.

More could be done in Wolfram Language, of course. The suggestions bar could be made more robust, and the function to roll up all the changes made with the suggestions bar could be made more robust. It should be possible to have a command like "Turn this into a function" or even "make these functions into a package". The idea is to make things as transparent as possible. There are some actions in WL that tend to break this transparency.

I used to write music. I started with this at a time when you had to use pen and paper. I welcomed even the most primitive software. However, none of it is transparent. Right now, with software like Finale, you can play on a keyboard (or use a microphone for a flute or Violin) to enter music. It is certainly more transparent than using the computer keyboard to enter one note at a time, but there are drawbacks. First, you need to be really competent in the instrument to make it work. Second, there is still an awful lot of work to clean up even the best transcriptions. Third, it works best for things like simple music or choral music. For complicated stuff, a composer still needs to have the fine control that only manipulating single symbols provides.

In a similar way, direct graphic manipulation to make code may be useful for a lot of simple cases, but there comes a point where only code will do well. For some things, such as 3-D plots or large data sets, direct manipulation would be much harder than code. What Wolfram Language provides is a faster, more intuitive (in the right hands) way to get things done with code.

Having said that, it would be nice to have more widgets for directly manipulating graphics in Wolfram Language.

Bret Victor frequency response of the filter example shown in the video (at 18:10 time), he has on his different web site, that one can interact with directly also. (bottom of the the page).

Of course, one can do this example and much more using Manipulate and Dynamics. Many examples at Demonstration site. But the nice thing about this example, is that it runs directly inside web page, and runs smoothly, with no additional installation of anything by the user.

If there is a way to compile Manipulate to Javascript (and any kernel code needed of course) and somehow be able to run Manipulate inside web page without any plugin, this will go a long way to make Manipulate more popular.

I agree with you that it is not easy at all. However, the thing Bret made is probably even so not that easy! I can't imagine another programming language where you can 'whip out' these kinds of programs, he shows some nice visualisation and 'manipulation software' (for lack of better words) but the code behind it is definitely not easy.

The examples he shows are very impressive, but also very very specialised! There is always a balance between those I think. Mathematica is less specialized but can certainly do the tasks he showed, but it will take some time to program them. But I'd bet it also took him quite some time!

I think quite the contrary, this is one of the best areas covered. The doc's page on Manipulate links to 5 very extensive tutorials. Plus Manipulate and Dynamic pages have numerous examples. And more than 10,000 examples on Demonstrations.

Bjorn Tipling, the author of the post If programming languages were weapons, would possibly answer "yes", as he sees Mathematica as "a low earth orbit projectile cannon, it could probably do amazing things" ;-)