Having really sophisticated memory management, type checking, semantics, safety guarantees, etc. is not at all trivial. The only part that has gotten easier is syntax => AST => machine code, but that is probably 10% of a PL if you want it to do something people will actually use.
Of course Jai "is fast" (meaning it has none of those things), so obviously LLVM is 90% of the work (just translating AST into LLVM calls). Yes, you can do this with AI in an afternoon, no its not useful to anyone. The real work of making a usable, interesting, useful language is not diminished, and it has little to do with the syntax => AST => LLVM part of the compiler.
Said another way, no one is choosing C, C++, Python, or Java because they are "easy ways to get generate machine code". They choose them because they have: superior semantics (design, memory management, portability etc), 3rd party libraries, frameworks, debuggers, ecosystem, documentation, support, standard library, etc.