> The worst part about uninitialized variables is that they frequently are zero and things seem to work until you change something else that previously happened to use the same memory.

This is not the whole story. You're making it sound like uninitialized variables _have_ a value but you can't be sure which one. This is not the case. Uninitialized variables don't have a value at all! [1] has a good example that shows how the intuition of "has a value but we don't know which" is wrong:

  use std::mem;
  
  fn always_returns_true(x: u8) -> bool {
      x < 120 || x == 120 || x > 120
  }
  
  fn main() {
      let x: u8 = unsafe { mem::MaybeUninit::uninit().assume_init() };
      assert!(always_returns_true(x));
  }

If you assume an uninitialized variable has a value (but you don't know which) this program should run to completion without issue. But this is not the case. From the compiler's point of view, x doesn't have a value at all and so it may choose to unconditionally return false. This is weird but it's the way things are.

It's a Rust example but the same can happen in C/C++. In [2], the compiler turned a sanitization routine in Chromium into a no-op because they had accidentally introduced UB.

[1]: https://www.ralfj.de/blog/2019/07/14/uninit.html

[2]: https://issuetracker.google.com/issues/42402087?pli=1