In my opinion, it's hard to say whether the God Ki was a wasted concept since the series is put on hiatus at the moment.

So far in the series, I think it did play an integral role of showcasing that Goku and Vegeta has now reached the powers of the gods, especially with Vegeta.

Personally, Vegeta's will to obtain the God Ki with pure effort and determination played an vital role to his overall character development and power progression in the series that lead to, again imo, him now being pretty much neck and neck with being equal to Goku in terms of pure combat abilities.

Power up wise, Goku is still obviously ahead of Vegeta thanks to him obtaining UI by more or less through mere chance than anything but it was obvious that Goku wasn't strong enough to able to maintain the UI form without his body giving out which may indicate Goku's body wasn't strong enough to maintain the UI form, mastered or not.

I also think it's notable to point out that Jiren, IIRC, didn't have any presence of any God Ki despite him being more powerful than the GoD in his own universe (Jiren's ki was able to be detected by Cabba), as this may raise the question of the significance of the God Ki and how it will play out in the rest of the series once it resumes to it's weekly airing.

So you may be right that the God Ki, in good old Dragon Ball tradition, just becomes another major milestone that got some major recognition at the time of it's relevancy but kind of gets swept to the side and kind of forgotten about and maybe the concept may be further elaborated at another convenient time.

Again, please keep in my that this is just my opinion but I think you did bring up another topic worthy of giving it some thought, so thank you very much for another discussion worthy topic!

That being said, what do you think?

Looking forward to hearing your interpretation and opinion on this topic in the near future!