There is a modern implementation if you feel like checking it out firsthand

https://jmvdveer.home.xs4all.nl/en.algol-68-genie.html

Not really, I did an implementation in the late 70s, ran on a mainframe of the time (1MHz 6Mb). The language itself is not much more than modern C in scope - and in fact many ideas that were new in 68 are expected in modern languages

The big problem was that the spec was essentially unreadable.

6MB was quite an amount back then.

Yup, we bought 1.5Mb of core for our B6700 for over a million dollars (I think we only had 3Mb on the machine I was working on)