The point of the Oxford definition is it broadly concurs with the MW one.
Of course it does. So does the Wikipedia article, and so do both of us. The difference is that you seem to think that the definition of kangaroo court is definite and objective, which it very clearly is not. I'm simply accepting that it can mean something slightly different to different people in different contexts without losing my shit about it.

Some people might argue that civil courts are kangaroo courts because they enforce contract law, which isn't actually enforceable in a practical sense. All a civil court can do is make judgements, they can't force people to cough up. You sue me successfully for 1 million, it's not like anyone can force me to pay it. What actually happens is I become legally bankrupt, the debt is written off or tied to potential future earnings that I might or might not make, and I don't go to jail or face any further consequence. Has any judgement been enforced? That's a matter of opinion. And so I could accept that someone using the term kangaroo court to describe a civil court isn't being wholly disingenuous, even if they are using that term for its impact rather than its meaning.