Its really not a **** move.
Don't concern yourself with the violator.
Your concern should be all the part 107 pilots out there trying to make a living, all the while facing new regulation after new regulation! You may feel guilty or you may feel...
If the Pilot is part 107 then Sorry but I would report them to the nearest Flight standards District office. If his work has not gotten him noticed already.
And that day you were in the circuit on downwind, might just be the moment that a stupid drone pilot decided to fly right across your path. I'm shocked as a past pilot, you feel it's fine for some idiot drone pilot to do that.
Because it's a dumb thing to be doing.
You probably don't realise that many aircraft don't have ADSB-out and your app won't be warning you about them.
And the planes that don't have ADSB are mostly smaller planes which are the ones most likely...
Not ALL aircraft have to send out that signal and what if that unit failed one day and was not broadcasting and you went to fly over the airport?
You are correct that if you fly over the centre of the runway there will be no aircraft right above...