Personally, I'm fine with it—but only because Regexps really belong to a different domain than people think.
Regexps do not exist to be a self-documenting syntax for writing code that gets read and maintained. If you are going to sit down, write, debug, commit, and PR some code that matches strings, for heaven's sake just write your pattern in BNF and apply a parser generator to it, or use a parser combinator library.
Regexps are intended as a fluent syntax for interacting with data. Regexps exist to be arguments to sed, awk, and vim's :s command. Regexps exist to let you type an SQL query into psql that finds rows with columns matching a pattern. They're meant to be a hand-tool, used by a craftsman during the manual work of analysis that comes before the job is planned.
And as such, regexp syntax features aren't meant to be composed into multi-line monstrosities that do all the work at once; they're meant to let you match chunks, and then pipe that to another regexp that winnows those chunks down, and then another that substitutes one part of each chunk, etc.
If you've ever seen a PERL script written in "imperative mode", where every line is relying on the implicit assignment of its result to the $_ variable, each line doing one more thing to that variable, each little regexp sawing off one edge or patching one hole—that's an example of the proper use of regexps. Such a script is effectively less a "program", and more simply a record of someone's keystrokes at a REPL.
And because of that, I honestly find it a bit strange that modern compiled languages build in "first-class" native support for regexps. They make sense in "scripting" languages like Ruby and Python because those languages can indeed be used for "scripting": writing code in their REPLs to do some manual tinkering, and then maybe saving a record of what you just did in case you need it again. But in languages like Go or Elixir? Why not just give the developer a batteries-included parser-combinator library instead? (If you, as a developer, need to parse regexps to support your users querying your system by passing it regexps, they could still be available from a library. But there's no need for a literal syntax for them in such languages.)
That being said, I wouldn't mind if an IDE for a particular compiled language accepted regular-expression syntax as a sort of Input Method Editor: you'd hit Ctrl+Shift+R or somesuch, a little "Input regexp: " window would pop up over your cursor, and then as you wrote and modified the regexp in the window, the equivalent BNF grammar would appear inside a text-selection at the cursor. That's a good use of regexps: to allow you to fluently, quickly create BNF grammars. As if they were a synthesizer keyboard, with each keystroke immediately performing a function.