I believe it is a Lisp related story, not some general truth. I mean, if I had a hashtable that needs to be mutated asynchronously, I'd probably create a single writer to it. Some entity that takes ownership of a hashtable and you can talk with hashtable only through it.

But if you are writing Lisp, and that hashtable is a global, then good luck ensuring that no one except the designated entity talks with hashtable directly. In particular, you can't force the user at REPL prompt to not do it.

The mutability lament in the same ballpark. Dynamic nature of LISP makes it hard to ensure that some code paths can't change values they deal with. Statically typed languages do it all the time: just pass a const reference into a function and you can be sure that it wouldn't change the value, or anything referenced from it. In LISP the easiest way is to make a deep copy of a value. Other ways would probably need some changes introduced into lisp-machine itself. So you are choosing between two alternatives: either copy everything, or to believe other code to behave like values are immutable. The former is slow, the latter just doesn't work generally.

Take Rust for example: if I have a mutable HashMap that needs a concurrent access, I'd hide it. It would be accessible directly in one module only, and the module would export safe API that you can't use to achieve data race. Technically I can make this HashMap to be global, but then Rust would rebels and force me to wrap my HashTable into a Mutex. If I added REPL to the mix, then REPL would need to lock Mutex as any other thread.

Lisp just an ancient language that doesn't have these guardrails, so you need to think things through and ofc you will be overwhelmed in any real case by all these things, and then you write that you can't have concurrency, interactivity and mutability at the same time. To have them, you have to limit yourself in how you write your program, and while you can use LISP to limit yourself, you still need to do the decision and invest some work into it. It doesn't happen magically all by itself. For magic you'd better try rust, though its "magic" requires months of fighting with borrow checker until it succeeds at conditioning you into right practices.