Was it? Once scale problems is gone -- you assume that all code can be checked out on one machine, and you have enough buildfarm to build all the code -- the most of the article's points no longer apply.
The downsides which still apply are Upside 3.3 (you don't deploy everything at once) and Downside 1 (code ownership and open source is harder).
And those are pretty weak arguments -- I would argue that deploying problems exists with polyrepo as well, and there are now various OWNERS mechanisms.
The fact the polyrepos are harder to open source is a good point, but having to maintain multiple separate repos just in case we would want to opensource one day seems like sever premature optimization.
The thing is, scale was only one factor listed among many.