What makes you think bombing in that video was indiscriminate? On the opposite, I see single buildings being destroyed, while the neighbouring buildings stay intact. That's a very precise strike by any standard. Furthermore, there is nothing to convince me these buildings were not occupied by Hamas terrorists (which are known to hide behind civilian population).
And yes, I agree with you that knocking on the roof is a very considerate "last warning". Which other country goes to such lengths to minimize civilian loss of life? There are early warnings, too, though: by phone, text and leaflets. That's why you don't see any people running out of that house: it is already empty.