SIMD is not a problem, it's hardware. Compilers tend to take advantage of the CPU-specific SIMD registers and instructions, or you can use them explicitly.

Writing generic SIMD code is more portable. C has libraries, and Zig also has vector primitives available through built-in functions.

Are there languages that "solve" SIMD?

Nothing if unsafe Rust is considered, though Zig does not require you to fight the language nearly as much. This is especially obvious with embedded. Zig's philosophy of no hidden control flow or allocation makes things simple. Simplicity is power.

For certain problems you would want a TLA+ specification for safety and especially liveness either way. It's not like Rust absolutely guarantees correctness in all cases.

Rust sits in a sweet spot between C/Zig and languages like Java, but it's not an appropriate replacement for either of them.

This is kind of a trick question because they are all Turing Complete, but so is Assembly. The best way to interpret your question, then, is not “what is possible” but rather “what is simple to express correctly” and “what is simple to get correct eventually”. Those are questions about how tricky it is to get something to compile in the language and which tools exist to help determine whether a compiled program does what’s expected and does not do what’s not expected.

The problem of a single allocation keeping a 4 KB page alive is something that you might commonly find with the C++ or Rust way of programming that encourages allocating many individual objects on the heap, but in Zig land this is pretty rare. In fact, compare a Zig implementation of a given application with an equivalent in any other language and you will find there is no contest with respect to the size of the memory footprint.

There are many cool possibilities that C++ has never explored and frankly I find your argument unimaginative.