It gets to a point when people need to face consequences of their actions and decisions.
You can empathize with them without putting yourself out there to help.
There is plenty on your plate to deal with, without the additional complexity of someone’s problems.
A diplomatic answer is “I’m sorry that’s the situation you’re in, but we currently don’t have the time and capacity to help”. If this person persists and keeps asking ‘why not’, maybe stop talking to them. ‘No’ is a complete sentence.
As we get older, we realise that not everyone is a positive addition to your life. Obligations to friends (and family) diminish as you start looking out for yourself and your family.