Smalltalk could do anything... which meant that it was really hard to adapt someone else's code to run in your context.
The more that someone modified their system, the farther it got from other people's systems, and the less applicable it was.
Self-decohering from collaboration: every unit of investment creates more of a bespoke rat's nest.
Previously, software was expensive to write, which meant you need everyone to run similar software to have some points of commonality so it can be reused.
That's why Smalltalk never took off outside of niche applications.
Maybe that changes in the world of LLMs?