You can't get a civil service job in Wales without a Welsh language qualification
Untrue. There are some jobs where fluent Welsh is a requirement. And plenty where it is desirable so you'd have a better chance. But the majority do not require Welsh.
However I always hear the 'I know x Welsh person and they don't speak/understand a world of Welsh! Waste of time' type comments.
This is also bollocks ime.
Every single person I know who grew up in Wales - from age 5 to age 80 - speaks or understands some Welsh. Every single person. Even if it's only colours, numbers, how to say/understand hello, welcome, thanks, toilet, road signs. Or how to smash out the Welsh anthem in the pub at the rugby 😁 They'll be able to read, speak, understand or pronounce something that someone growing up over the border couldn't. It's far from wasted imo. It's ensuring the language, culture, heritage of Wales doesn't die.
You'd need to be especially dense to grow up in Wales and literally not understand or speak one word - it just doesn't happen ime. And I live in S Wales where Welsh is far less spoken than further north.