In principle there’s no reason why you can’t profile the code ahead of time with a representative benchmark of the application and perform most of the important

In principle there’s no reason why you can’t profile the code ahead of time with a representative benchmark of the application and perform most of the important optimizations that a JIT performs, and then save that generated code. In fact V8’s snapshot mechanism effectively does that with the Chromium APIs. However you’re losing one of the significant benefits of these languages (that is pretty much crucial in the JS case): the ability for them to be written independently of the particular runtime and architecture of the execution environment. Code generated for JS (just as an example) has to be intimately aware of the runtime’s native bindings and GC implementation to be as efficient as it is in modern browser engines. You would also lose the ability to software sandbox untrusted code. Basically, the JIT platform for which exploits are the most valuable by a large margin wouldn’t be able to use this solution, and the other JIT platforms aren’t often used in ways that make this kind of issue relevant in practice.