I think there's a lot to this. I work in a creative industry — definitely not 9-5 — and I agree with the point that mumsnet has a bias towards doing safe, predictable, normal things. I think a lot of life coaches really do help people out... but even those that do a good job of it often make a very marginal income.
On this thread, no one is saying they have a problem with a job not 9-5.
What they are saying me included is that many many 'life coaches' are themselves life failures and unqualified to coach. Like I said above, you wouldn't have tennis coaching from someone who couldn't demonstrate they could play tennis well and to an above average standard. No one should be 'life coaching' unless they have achieved above average and have track record of having attained a good life for themselves. Too many people turn to this as 'something else to do' because its basically unregulated, we all think we are qualified to give strangers our opinion and advice and because they are bummed out with their own life.
That's the problem with life coaching as a job. So if someone pitches up chewing on a piece of straw in a floaty dress twirling a strand of hair round their finger sighing 'I'm fed up with my low paid job and useless life, I think I'm going to become a life coach" they can set up in an instant and no one can stop them. Plenty do and that's why as a job it has a bad rep.
There are some good ones but like the link I posted above, they tend to be high achievers who have then fully committed to training and developing their own methods on the back of that training. Not bored housewife switching on a whim. (not saying that is the OP btw) so if someone arrives here saying that what they want to do, they will get a hard time because there will be an assumption that they are in the pray and a whim category of life failures until they say otherwise.