It is slow. Nobody would deny that. It also requires work to avoid disastrous compile times, that's also true.
But 15 minutes? Even rustc doesn't take that long (on a powerful computer), and that's a very large program that is compiled at least twice (bootstrapping)! That's just poor engineering, not knowing how to write fast-to-compile Rust code.
You can't compare rustc to a large application. Yes it's a large program, no it's nowhere near as large as Codex CLI. 1420 crates.
I just did a release build of Codex CLI with "lto = false" for codex CLI binary and code mode host only, and it took 75 minutes, of it 1063 seconds for the final rustc of codex bin. Windows Defender off. That's on a 4-core 2021-era Intel laptop with 32GB RAM and a half-TB SSD. And I can't let the build run at default concurrency, because rustc OOMs the machine, so this is with cargo jobs = 4. Regardless, the final rustc call is independent of that and that was 1063s with lto=false. Previous build was 90 minutes with default thinlto for the same CLI build.
How can Codex write fast-to-compile Rust code, do tell?? Do tell!