I've recently become more assertive too. Etcetera1's post is excellent.
I'm in my sixties and for many years have endured my mother's poor behaviour. Last year, I reacted and we're only now starting to rebuild the relationship. It will never be good; it wasn't before anyway.
To me, it took the pandemic and the advice of a new friend, to realise that I was not a doormat. However, it's harder to make improvements when dealing with family. There's a mental block because of being blood relatives.
The choice is clear. Do you go on being the subject of criticism/ridicule or change so that you assert who you are. In my case, another problem has been the lies told and incorrect assumptions made about who I am and what I'm doing. I'm a person in my own right and will not be trampled on by others who want to control.
Stay true to yourself and continue the good work