Ok..so here is my theory based on what I know. I think with 4, EA hedged its bets a bit. They didnt want to pour a ton of resources into the game because at the time they werent sure if this was going to be the last EA/UFC game. Covid also played a role a bit in what they could do from a mocap perspective and that held the game back.
With that said, I'm not optimistic we will ever get the game we want. I think there will be sim focused changes around the edges but the focus will likely be the same as UFC 4 going for the future. The sales of the game justify that approach for EA.