You think Yvette Cooper is dreadful? I think you must mean you find her politics dreadful, because her ability is obvious and she also has backbone - absolutely showed her arse to that tribe of Yorkshire pygmies she represents over Brexit, at some personal cost in terms of harassment and threats of deselection, and still got returned in the general. But sure, I can see she's not everyone's cup of tea for labour leader and it wasn't the right time. Still would have been 1000 times better than JC, mind.
Vice versa I don't mind Corbyn's politics but think he's a dreadful incompetent, so his politics don't matter as he can never realise them. Up to you if you want to peddle the fantasy of him influencing the scope of what's possible, I don't think anyone is seriously going to challenge you there as we all have respect for the grieving process. The left has just been annihilated at the ballot box so some straw-clutching is inevitable to try and make sense of the whole thing.