I'm not entirely sure that work/life balance means poor mental health though, I don't think anyone's claimed that but it almost reads that way. It certainly could lead to that, but I'm not rushing to say thats the case by default. A 40 hour work week is plenty to cause mental health issues depending on the job.
I'm not saying that its a guarantee but having extra time to work on yourself does make things more manageable on average.
But that's just priorities. I have someone in my life that needs mental wellness - needs to work on themselves - as bad as anyone I've ever met in my life. She even knows it. But her claim is, "I don't have time; I have two kids, work, blah blah blah". But she also goes on like five Tinder dates a week. Dude (Dudette?), grow the fuck up. Being an adult isn't doing whatever you want when you want, being an adult is doing what you HAVE TO DO WHEN YOU HAVE TO DO IT, without being told.
We are a society of excuses. I don't think I'm out of line in saying "if you can, then shut the fuck up and do it". The number of people who truly CANNOT - as opposed to "won't", or "don't want to" is exceedingly low. We talk so much about stepping up and having your back and "Boston Strong!" and all these memes about whatever, and yet when the rubber meets the road it's "oh, this is too HARD". I have little sympathy for that, frankly.
(Again, to be clear, I am NOT including those who truly cannot. I am sympathetic to that.)