It is just my opinion from what I have seen
She seems very insecure and for me, the fact that she is incapable of being single just reinforces my opinion.
My mum is actually someone who hates being single. She requires the validation that comes with being in a relationship (don't worry, she doesn't know my ds name lol).
Thankfully she has made better choices than KP, but during the gaps between the long term relationships with nice, suitable men, she would literally go out with anyone just so she was in a relationship. Most of them men that she would never normally look twice at, and who had very different lifestyles and hobbies.
One guy she actually converted her religion for a few months and changed her name, and another from years ago was recently put in prison for stalking a woman and stabbing her horse!
I don't feel I have spouted any vitriol at KP so I presume that wasn't aimed at me personally?
I think teh reason Kate Winslet doesn't attract as much criticism, is what you already acknowledged in your post. Katie appears to make sudden and rash choices, and puts them out into the public domain.
I don't know much about Kate Winslet (and that kind of says it all with what we are discussing) but perhaps if she was so public with her private life, people would be critical of her too.