Trying to simplify something that doesn't simplify inherently isn't always a good idea. Regex is pretty close to the least level of abstraction that is necessary to get the job done. It could probably be improved on, but probably not by much.
Some commenters below mentioned this Java syntax is a good idea and using endless number of regex cheatsheets as a testament to why regex is not simple enough and should be replaced. It's almost silly that this is even an argument on HN. Take for example quantum physics, there are lots of videos and guides that try to explain how it works, in fact some of the smartest people tried to explain it, even Richard Feynman. But he famously said if you think you understand quantum mechanics you don't understand quantum mechanics.
Some things cannot be reduced any further, this does not mean those things are always simple in nature or somehow were designed in a convoluted way on purpose.
At least when it comes to regex it's important to keep in mind what Einstein said, "everything should be as simple as possible but no simpler."
It's ironic that people apply reductionism to simplify regex, a thing that itself one could argue is a prime example of reductionistic design, yet they complain it's too abstract while applying reductionism.