Bob Erb: "The out-of-the-box UI is very old-fashioned"

Bingo.

In addition to the above (which affects Squeak more than it does most other
Smalltalk dialects,) Smalltalk's main problems have been:

1. Lack of a sponsor with sufficient marketing muscle and/or commitment.
2. Competitors who falsely claim to be essentially equivalent--but who do
have a sponsor with sufficient marketing muscle/commitment.  These
competitors also cause problems because they redefine the language Smalltalk
uses to describe itself, so that it is harder for observers to clearly
discern how Smalltalk is different.
3. The perception that Smalltalk is "old," "slow," "a failure" and "weird."
4. The name of the language.
5. The balkanization of the language into numerous dialects.  United we
stand, divided we fall.
6. The refusal/failure of many Smalltalk dialects to address fundamental
issues such as modules and namespaces.

Note that I did not list Smalltalk's syntax.  That issue is a red herring.
Were that not so, all successful languages would have the same syntax as
either COBOL, FORTRAN or BASIC.

--Alan