Yes I've seen delays like that... had a few out of BHX when security (or what passes for security) got swamped and we had a 40 minute delay for our pax... had to depart as if we hadn't, we would have arrived after our destination closed. Such a delay could also be slot-induced. Do you have all the facts regarding that flight? Do you know all the curcumstances? Thought not.
And do you know all the circumstances regarding the events the next day? Do you know, for example, whether an imbound aircraft intended to sort the problem out was delayed by a slot... or weather... or a tech problem? Maybe a lack of de-icing capability, or Swanwick dying again, or Eurocontrol having a brain fart? Possibly a crew member being in a traffic accident? There could be hundreds of reasons, none of which necessarily indicates a management failure.
Panning an airline on the basis of one experience is ever so slightly over the top.