Overall, I think the problems areAre the problems in Standard at all related to them changing the block format, losing small sets, and having to develop every set with a relatively high power level because they're meant to be standalone?
* Pushing green and green-blue's power in many directions that add up. It's not just Oko, but also Gilded Goose, Wicked Wolf, Once Upon a Time, and Hydroid Krasis.
* Really overestimating how easy it was to kill planeswalkers.
* Reacting to powerful threats by printing even more powerful threats to counter them but also making them generally powerful so they just get played instead or in addition. We know for a fact that 3feri was printed to counter Nexus of Fate. Oko's loyalty was likely from (1) designing Questing Beast, (2) seeing Oko dies too easily to Questing Beast, (3) making Oko more powerful so he doesn't die too easily to Questing Beast, (4) forgetting why they designed Questing Beast and Fry in the first place.
Also,