Yup. Regex is not a silver bullet for "match stuff", and it is wrong(ish) tool for following jobs:

- context sensitive matching

- matching with multi-char-exclusions

(regex is happy the most, when it's used to match "regular language" things)

Know saying wrongish, but for multi-char-exclusion matching, can't you just do [^chars]?

So to search for words without any vowels just 'grep [^aeiou]'?

It's semantics, not syntax. It's one of the simplest and oldest search engines in the history of computing; obviously a more complex engine can provide more robust semantics.