Learning Rust is at least an order of magnitude harder than learning Smalltalk. This is not to dismiss what you have said. On the contrary, it highlights what must be an enormous miss in how Pharo presents documentation on its landing page.
You have Smalltalk the language, which is this [] big, and Smalltalk the environment and class libraries, notably the GUI system, which is this [.....**.....] big.
And, sure, you have all of the source code, but, for me, the source code may as well be organized in a stack of index cards. You get the individual methods, but not the sweeping picture. I can learn a lot more scanning a file full or source code, compared to the little snippets of code you're presented with screen by screen. Just being able to scroll and absorb is useful.
But even then, especially being OO, with lots of abstraction, tracing through the GUI code, blind, is very difficult. You end up at top level, "do nothing" abstraction classes. Much like in Java, where everything you click on is an interface, which doesn't tell you a whole lot.
Navigating a Smalltalk image is a skill all its own.
Finding documentation to learn to use this absolutely obscure system is near impossible. I seen an announcement about a Pharo release a couple years ago and was like "huh, that sounds cool." Proceded to download it and had no clue about anything. It is not at all like any other IDE.
Learning it might not be hard, but when the IDE is absolutely different from anything else you've ever used, combined with very little documentation that speaks to how to do the basics, it can be a very mysterious and difficult thing.
Rust is like any other programming language, in that you write code in a file, then compile it. Yes, there's other stuff to deal with in between and it can get way more complicated. But the IDE is the real culprit, combined with documentation for a developer to learn to develop real applications with, that makes Pharo infinitely more difficult in my personal opinion.
I guess to simplify this a little with an edit. If you already know another programming language, learning Rust is not fundamentally different. Some parts of it will be difficult like the borrow system and stuff that's very Rust centric. But in most ways it behaves like a lot of other languages in terms of using it at a bare bones basic level. Pharo is ... otherworldly in that nothing else really compares, you have to learn a completely different paradigm for how to program it, and that is the difficult part imo.
I think there is a valid reason for tools like Pharo to exist, I don't know the answer to how to improve the situation outside of a (selfish) desire to see better beginner documentation that talks about using it for people that have zero knowledge of Pharo and similar tools. Explain it like I'm 5 type stuff. I suspect it all becomes easier once the general primitives are explained but until they are there's an inscrutability to it.
I think that's a pretty neat introduction to the very basic basics.