I will make an important nit. Keep in mind this is a nit. It's text in bold in the page, but this is NOT an attack on anything else in the article, which describes good design practices.
There is no principle that one should "Choose the least powerful language suitable for a given purpose."
This would, in fact, be an incredibly stupid principle. One want the most powerful language for any purpose. However, "purpose" is broadly defined:
1) We want code to be semantic. This allows a11y tools, search engines, and various performance optimizations to understand what's going on.
2) We want clean abstractions. In a horizontally-abstracted system, we would like the content designer to be focused on the content, the UX designed to be able to focus on the UX, and the back-end engineer to be focused on the back-end. (Note that, contrary to the beliefs of most people who have only worked on database-backed web applications, vertical abstractions are okay too, and break things up completely differently).
3) We want systems to be bug-free and understandable.
This can leads to programming paradigms like functional programming + React, where no mutation is allowed. This isn't a random restriction which reduces power; to the contrary, it increases power by allowing predictable state, avoiding a whole class of bugs, and allowing debugging with time travel.
In other words, you want good design discipline. However, the point here is much more on "good design" and not "discipline."
Every one of the changes proposed can be derived from first principles from the above. But this does not come from some principle of "least power."
To make this even simpler: Think of diet discipline. The goal isn't discipline about being hungry and eating yucky food. The point is about being healthy and losing weight. That probably involves being hungry and eating yucky food, but that's not the point. Food should be as tasty as possible and people should not be hungry to the extent goals on weight, heart health, insulin resistance, etc. can be accomplished.
Same thing here. Languages should be as powerful as possible, while allowing goals around readability, introspection, a11y, abstraction, etc. to be accomplished. That requires very specific and narrow constraints on what one bans.