Thanks for the paper link.
> My understanding of the more fundamental problem is related to how IQ tests attempt to quantify intelligence as a reliable predictor of future success.
This was indeed the original motivation in the past.
The fact that most variants to define the concept of "intelligence" in some kind of replicable test lead to to the observation that all of these concepts are strongly correlated with the g factor, so in my opinion the evidence is on the side that we formalized "intelligence" mostly correctly.
Now that we have a decent measurable concept of intelligence available, we can actually do studies with which other things (such as "future success") intelligence/IQ is correlated. And here the results are in my opinion, well, ... somewhat complicated.
For example, as of today, it is quite well-known that if you consider having a steep career as "success", it's rather that being in the dark triad is quite helpful.
Another example: it is well-known that attractive people are often thought by other people to be more smart than they actually are (halo effect; https://en.wikipedia.org/wiki/Halo_effect#Role_of_attractive... ; see also https://en.wikipedia.org/wiki/Physical_attractiveness_stereo...).
Thus: the problem rather seems to be that intelligence/IQ is not a predictor for quite some things that people would love it to be associated with. But this is in my opinion not a problem with IQ, but with social expectations.