Only when not using one of the many Lisp editors that exist since Lisp Machines (Symbolics, TI), Interlisp-D (Xerox), that survive in Emacs SLIME, Cursive, LispWorks, Allegro Common Lisp, Raket, VSCode Calva.

Not true at all IMO. Reading code is reading code regardless of whether you have a fancy IDE or not.

S-expressions are indisputably harder to learn to read. Most languages have some flexibility in how you can format your code before it becomes unreadable or confusing. C has some, Lua has some, Ruby has some, and Python has maybe fewer but only because you're more tightly constrained by the whitespace syntax. Sexpr family languages meanwhile rely heavily on very very specific indentation structure to just make the code intelligible, let alone actually readable. It's not uncommon to see things like ))))))))) at the end of a paragraph of code. Yes, you can learn to see past it, but it's there and it's an acquired skill that simply isn't necessary for other syntax styles.

And moreover, the attitude in the Lisp community that you need an IDE kind of illustrates my point.

To write a Python script you can pop open literally any text editor and have a decent time just banging out your code. This can scale up to 100s or even 1000s of LoC.

You can do that with Lisp or Scheme too, but it's harder, and the stacks of parentheses can get painful even if you know what you're doing, at which point you really start to benefit from a paren matcher or something more powerful like Paredit.

You don't really need the full powered IDE for Lisp any more than you need it for Python. In terms of runtime-based code analysis Python or Ruby are about on par with Lisp, especially if you use a commercial IDE like Jetbrains. IDEs can and do keep a running copy of any of those interpreters in memory and dynamically pull up docstrings, look for call sites, rename methods, run a REPL, etc. Hot-reloading is almost as sketchy in Lisp as it is in Python, it's just more culturally acceptable to do it in Lisp.

The difference is that Python and Ruby syntax is not uniform and therefore is much easier to work with using static analysis tools. There's a middle ground between "dumb code editor" and "full-power IDE" where Python and Ruby can exist in an editor like Neovim and a user can be surprisingly productive without any intelligent completion, or using some clunky open-source LSP integration developed by some 22 year old in his spare time. With Lisp you don't have as much middle ground of tooling, precisely because it's harder to write useful tooling for it without a running image. And this is even more painful with Scheme than with Lisp because Scheme dialects are often not equipped to do anything like that.

All that is to say: s-exprs are hard to deal with for humans. They aren't for humans to read and write code. They never were. And that's OK! I love Lisp and Scheme (especially Gauche). It's just wrong to assert that everyone is brain damaged and that's why they don't use Lisp.