The two problems with this were a lack of performance and the difficulty of understanding other people's code.
Dan Ingalls looked at the most popular styles people had created in Smalltalk-72 and defined a fixed syntax for Smalltalk-76 with the same flavor. This allowed him to "compile" -76 into bytecodes which would then be executed much faster by an interpreted virtual machine (and years later a JIT compiled one).
The analogy is putting grass everywhere in a new university campus and after a while seeing where the grass has been trampled and putting concrete sidewalks there.
For Smalltalk-80 they wanted people to be able to use it on their own computers and not only on the special Xerox PARC ones so the patched the syntax to use ASCII instead of their own character set. That made it uglier, in my opinion.
I can understand many people not liking the Smalltalk-80 syntax, but we do get some new people to the language every year and quite a few of them find the syntax one of the nicest features.