I don't think Donaldson had a game he will look back on as representing his best, but I also feel like on here (and many places you find rugby chat) people think a player swap is the magic solution for all poor performances. That game had a number of issues that were not to do with just Donaldson.
Donaldson has so far this season been swapped to Fullback and played most of it there, played last season I believe about 12 games, started about 8, I don't believe all at Flyhalf with Tane getting a decent chunk of time. I can see how this performance could have resulted. How for a young aspirational flyhalf who found himself in the Wallabies, this could be playing on his mind even. I don't personally think Donaldson was ever the best natural flyhalf, that was always Harrison for me, but he is still better than this.
We saw the same with Gordon Carter not performing last year in his 13 appearances, which at least I believe were mainly at flyhalf and then this year getting a starting run to really find his form. Our players get so little time to find themselves compared to some of the other competitions around the world. Add in chopping and changing and I'm not sure how we ever expect them to truely grow in certain roles. I mean I get it, it's a short season and a results business, but still.