Tbf I hadn't seen it yet zoomed like that, frame by frame; I'll agree that looks a lucky one. If I were the TV umpire I'd be giving it not out regardless of the soft signal.
I disagree with doing away with the soft signal though. We should all be familiar with camera foreshortening by now, and it's not always possible to give a definitive answer either way. In those cases, I think it is better to defer to the initial first reaction (i.e. what would have been given for the 100 years pre-dating TV umpires). Therefore in this case, it's not the rule that's wrong but the application, there is enough evidence to overturn the on-field decision.
There are enough camera angles now to get rid of it entirely. The most silly ones are where it's a diving catch in the deep. The umpire standing miles away is expected to make a judgement and give a soft signal. Just send it straight to the third umpire. It's insane, and not really fair on the standing umpires either tbf.