This great idea of Lisp (the simple syntax of function calls in round brackets) isn't much different than a good macro assembler even back in the 1960's. The only major difference was that more than 1 function could be defined in 1 source code line. (I think that machine code is nothing but a sequence of function calls where the function is the logic encoded in the CPU itself for each opcode.) Is it fair to compare the complexity of expression evaluation etc (Fortran) with a macro assembler? Obviously any program can be coded in a macro assembler and therefore that would also be true from a syntax like Lisp.
When I was in my 20's, I programmed at least 100,000 lines of Z80 assembler for the first micro computers. One project was at least 40,000 lines and so I know how difficult it is to program larger assembler programs. The biggest problem is that it is hard to see the structure of the loops and conditionals that we normally indent in higher level languages. (You can indent a Lisp program in any way but the language doesn't require any at all.) It is also difficult to recognize expressions. Both of these problems are also there in Lisp (unlike most other high level languages).
One last point about the linked list structure at the heart of Lisp. Linked lists are poorly executed in modern computers that rely heavily on locality of data, to optimize the L1 cache. Lisp was very easy on the compiler/interpreter writer but wasn't very good at optimizing the readability of the code for the programmer. (I don't want a religious war but I will point out that most programmers have never programmed in Lisp even though it was one of the first computer languages created.) Before I get a lot of dissing comments, I think with practice, some programmers developed an eye for the lack of structural clues and made some reasonable size code. You could say the same about some programmers making quite good large scale programs in assembler but that doesn't mean that writing in assembler or Lisp should be encouraged.
When I was in my 20's, I programmed at least 100,000 lines of Z80 assembler for the first micro computers. One project was at least 40,000 lines and so I know how difficult it is to program larger assembler programs. The biggest problem is that it is hard to see the structure of the loops and conditionals that we normally indent in higher level languages. (You can indent a Lisp program in any way but the language doesn't require any at all.) It is also difficult to recognize expressions. Both of these problems are also there in Lisp (unlike most other high level languages).
One last point about the linked list structure at the heart of Lisp. Linked lists are poorly executed in modern computers that rely heavily on locality of data, to optimize the L1 cache. Lisp was very easy on the compiler/interpreter writer but wasn't very good at optimizing the readability of the code for the programmer. (I don't want a religious war but I will point out that most programmers have never programmed in Lisp even though it was one of the first computer languages created.) Before I get a lot of dissing comments, I think with practice, some programmers developed an eye for the lack of structural clues and made some reasonable size code. You could say the same about some programmers making quite good large scale programs in assembler but that doesn't mean that writing in assembler or Lisp should be encouraged.