Some people just need to complain
No matter how good their life becomes, some people will find things to complain about. It doesn't matter where you put them. What you change about their life. They will crib. They will find things going wrong in their lives and rant about it.
The problem is not their situation. It is not the people around them. They fail to realize that it is them. They are the problem. They just cannot look at things any other way.
When you come in touch with these troubled souls, understand this. Do not try to suggest solutions to them. They will refuse to see it. Instead just listen to them. They will go their entire lives like this. It is not on you to solve their problems. Unfortunately some of these people might be good friends of yours. All you can do is listen to their problems. But don't take it to your head or get too immersed in them. Even they don't. When one issue is fixed, they will move on to another.
It can be tiring. Just draw some boundaries and look at the positives in these troubled souls. More importantly, it is a warning to you. Never become like them.
Life will always have problems to deal with. It is about how you handle it with grace. No amount of complaining will solve your problems. Learn to enjoy life as is. Don't spend the rest of your life looking for things to rant about. Then on your death bed you will remember that all this while you had forgotten to live.