> This post makes it seem like the pass ordering problem is bigger than it really is and then overestimates the extent to which egraphs solve it.

It isn't so much for SoTA implementations like LLVM, but it is for HL IRs like those present in MLIR. For LLVM, you're basically always in the same representation and every pass operates in that shared representation. But even then, this is not quite true. For example, SLP in LLVM is one of the last passes because running SLP before most "latency sensitive cleanups" would break most of them.

In particular, HL to LL lowering pipelines suffer very heavily from the ordering concerns.