Speaking on behalf of the superficial camp, I admire the Rust core regex focus on linear performance and I can well believe that it is based on recent theoretical work.

Splitting the regex features between some core ones that meet a DoS standard and some non-core modules that do other "convenience" features makes sense as a trade off for Rust. It would not make sense in a scripting language like Raku where the weight is on coder expressiveness and making it easier / faster to write working code.

I seem to have hit a seam of intense implementation guys - and they are holding their own since they know their stuff.

I think there is room for improvement BOTH with new system language / core performance innovation AND with advancing the PCRE regex syntax (largely unchanged since the 1990s) and merging it seamlessly with standard language support for Grammars.