> Except that that whitespace is not used only for that purpose, it could mean also something else, right
It's not just whitespace, it's the specific formatting of whitespace. It's just a character, like any other, only defined by it's lack of distinguishing characters. Instead of whitespace, block continuations could be defined by pipes, or angle brackets, or any number of things. They chose wihtespace.
> We trade an unambiguous set of characters --the parentheses-- by whitespace, and make it context sensitive.
Parenthesis are often context sensitive in languages. It's very common for them to handle both code block and object/dict/hash definition. Languages often use '+' for both numeric addition and string concatenation (which in my eyes is often more problematic and less justified than whitespace as a block defining element).
> How is that now more readable? As someone who has had to match these whitespace based parenthesis I can tell you it's not more readable.
"Readable" is subjective. Unless you have experience with it, you would probably find APL more than unreadable, likely impenetrable. Experience can vastly change what one find easy to understand, and easier to learn doesn't necessarily mean better in all respects.
> It's more like someone determined that parenthesis were not visually palatable and decided to remove them.
Or, it actually is that some people prefer it, even if you and I do not, and that's what it is, a preference implemented in the languages they decided to make. It is, to me, subjectively worse, but the key word there is subjectively. There are trade-offs between the benefits and detriments of that style, but we shouldn't fall into the trap of assuming we can make objective claims as to the quality of the choices of languages that prefer structured whitespace as a syntactic element when it's obvious a large percentage of people find it beneficial.
In the end, unless you're being forced to use this language, I'm not sure why it matters what choice they made with regard to this. If you don't like the choices made by this language, don't use it, and your actions will speak for themselves. If enough people feel that way, the language will die out or change. If enough people do like it how it is, it will continue, as it should, because there's no reason we should restrict other people's choices when it comes down to what is by large an aesthetic choice.