Lisp operators are distinct from functions. It's just that arithmetic operations are functions; Lisp dialects use operators for various other constructs that cannot follow the function call evaluation rules.

C++ sort of makes operators functions. Any overloaded operator is a function. If a is a class object then a + b can be spelled otherwise as a.operator+(b). This doesn't work for the built-in definitions of the operator, as in 2.operator+(2).

The built-in + operator in C++ can also do things that used to be impossible in C++ until its template system became more powerful. Namely, the result type of the built-in + is deduced from both operands and can be different from both of them. If C++ were being redesigned clean-slate, it would likely be that operator overloading is allowed for the non-class types like int, and all the built-in operators are defined in terms of templates, whose deduction/instantiation reproduces all the rules.