Honestly, I think regular expressions look more difficult that they are. Partly this is because they are easier to write than to read, although that tends to make learning them tricky.
Regular expressions are a lot like Keyboard Maestro - the basics are easy to learn, and then each new concept adds to all the rest.
Just like macros are made up of a sequence of actions, regular expressions are a sequence of tokens, and just like there are lots of different kinds of actions, there are lots of different kinds of regular expression tokens. These are all referenced via the Keyboard Maestro Help menu to the ICU Regular Expression documentation.
The simplest token is just a character like a letter or number which just matches itself (possibly case sensitively, possibly not).
Common other ones are ^ (matches the start of the line or text), $ (matches the end) and “.” which matches any character. Another common token is the [pattern] (eg [a-zA-Z0-9] matches any letter or number). You can also use brackets to group together a sequence of tokens into a single token.
After a token you can have an an operator like * which means “zero or more of the preceding thing” or + which means “one or more of the preceding thing”.
So for example:
matches text that is one or more sequences of abc ant nothing else (like abcabcabcabc).
Now sure, there are lots of tokens, lots of operators, lots of expressions, and then there are flags which let you change some behaviour (like case sensitivity), but still, the basic concepts are pretty straight forward and you can learn more as you go, and get a lot of value knowing only a few of them.