According to https://algol68-lang.org/, and as expressed in the recording, the contributors (specifically Marchesi) believe that ALGOL 68 continues to have advantages over other languages to this day ("more modern, powerful and safe" and "without successors"). One mentioned in the video is that the more complex, two-level grammars allow properties that would usually be described in the semantics of a language to be formally expressed in the syntax (the example he gives is the behaviour of numeral coercion). I guess this is not a surprise, as van Wijngaarden grammars are known to be Turing complete, but nevertheless it seems like something interesting thing to investiagate! There is a lot of lost wisdom in the past, that we dismiss because it doesn't fit into the language we use nowadays.