Some people will never be happy. They aren't happy in their airline career but if they switched back to a 9-5 job you can bet it wouldn't be long before they found something to complain about there too. The grass is always greener.
As for me I have enjoyed my career so far as a regional pilot. Do I look forward to the possible future of a legacy? Absolutely. But I'm not going to live every day hating what I do now just for a hope for something better in the future. That's how you end up like RyanP above.
There are obviously very different experiences for each person. In my case, I haven't worked a weekend in nearly a year and get plenty of days off each month. This month I have 16 days off 92 hours. Next month I have 15 days off 89 hours..and I'm not even very senior.
That being said, it isn't always the norm. I have some months that I only get 12 days off.
Point is it is what you make of it. It definitely isn't the career fit for everyone but I would say on a daily basis the majority of people I fly with really enjoy what they do.