I'm pretty sure new PBNs are dead (those built on 2017), they do not work anymore.
But PBNs built on <2016 still works.
I'm using PBNs from different years now and everyone of them actually ranked me with no problem.
On May 2017 I started my first project of 2017... and simply it doesn't work.
I published the contents on May and started my PBN campaign on 1st July 2017.
I almost drop 10 PBN backlinks over the last 1,5 month and serp didn't changed a bit.
There are crappy domain with crap content and 0 backlinks (and they are not using PBN, probably they do not even know what PBN are) on page 6 and they actually outrank me.
My domains are not spammed and my PBN is powerful enough, as I said I have quite some experience now.
And if the power were the problem, still I should outrank crap domains with no contents and no backlinks don't you think? I would have more power than a brand new domain for sure.
And onpage is good for sure.
The following you can see my serp changes. serp keep always the same from mid May