Here is my take
Liam saw himself as the Gary Barlow figure of 1D. I think Liam has had a hard time accepting that is not the case. He became arrogant and it’s been hard for him to undo the damage that arrogance caused to his reputation.
Harry has managed to become successful through sheer hard work (can’t be denied) good PR and managing to create an illusion of himself. The reason why Harry is so popular is because he has created an air of mystery around him, he rarely opens up about anything personal and uses a lot of deflection back onto his music. Harry is confident and self assured that’s why it works for him. Liam is not. He is an impulsive over sharer who has become cringy through trying too hard and instead of getting his head down and creating a real career he was off partying in vegas and enjoying the ego trip of being in 1D far too long - longer than the others did. He found it hard to let go and become who he wanted to be, and he still doesn’t know.
Zayn for me is the best singer, I love his voice and music but he is the absolute opposite to Liam - Zayn wants to make music but hates fame. Liam wants to be famous more than he loves music. You can tell Zayn loves making music he is good at it and really spends a lot of time working out what works for him. Harry seems to enjoy
performing music
Louis I feel sorry for and I don’t think he’s particularly talented singer and that’s been hard for him, he is not a strong singer and has a hard life. I hope he finds what makes him happy as it must be hard to see others around you do better and be working very hard yourself.
Niall seems very grounded and has a good sense of self, is able to balance himself and is coming out as a very good singer/songwriter as he’s relaxed and not pressuring himself to be someone he isn’t, he knows what his limits are and he is making great music I really like so much of his work. It’s not setting the world on fire like Harry but that’s ok - you don’t always have to be the best to still be good at something. Niall has a long career ahead I think as he gets better at what he’s doing.
Liam I suspect just can’t find what he is looking for and he’s drifting around. He looks weird now and I think he’s not a good or present father at all. Being a dad seems to have pulled Zayn out of whatever serious addictions he was battling and that’s good to see.