"pyès" is not outdated. How could it be?
What you will find is that people from a specific region of Haiti tend to use "pyès" more than others.
You are correct to say: M pa't wè pyès moun la.
Other synonyms for pyès moun are: okenn moun, pèsòn
So, you could also say:
M pa wè okenn moun la.
M pa wè pèsòn la.
Also Creole speakers will use pyès to mean none as in:
There will be none of that.
P'ap gen sa pyès.
I have no money on me.
M pa gen pyès lajan sou mwen.
She doesn't have any children in Haiti.
Li pa gen pyès timoun Ayiti.
I have no money on me.
M pa gen pyès lajan sou mwen.
She doesn't have any children in Haiti.
Li pa gen pyès timoun Ayiti.