The format change reduces the stakes for me of the group stage games, so every game feels much less like they matter as much. It's much easier to follow, permutations wise with a 16 or 32 team setup because you know your teams likely path to the final.
I'm still excited about the tournament and will watch as many games as I can, but it is almost as if the tournament doesn't really get interesting until after the group stages, which is a shame.
I do think football fatigue comes into it as well, there are increasingly too many games to follow and keep track of now.