But the documentation was a huge barrier
--all the familiar ideas were given completely new (and unintuitive) names, making it very difficult to get into.
I may be biased in my view, but I think one fatal mistake that A68 made
was that it had no scheme for porting the language to the plethora of
computers and systems around at that time.
(The Bliss language from CMU had a similar problem, requiring a bigger computer to compile for the PDP-11).
Pascal had P-code, and gave C a real run, especially as a
teaching language.
Nowadays, newer languages like Python just piggyback on C or C++...