There’s just no consistency from game to game... Referee interpretations vary from staff to staff depending on which crew is in charge for any given match.
If goalkeepers are required to be on their line for every spot kick, then you need to hold them to that standard every game. If players are not allowed to encroach during a penalty, then you need to hold them to that standard every game.
I don’t think anyone has a problem with technology assisting officials to ensure that calls on the field are correct— the problem lies in the fact that it’s use varies from game to game, where even after seeing an HD slow motion replay from multiple angles, fans watching at home are left to guess what the referee interpretation will be.