One thing many overlook is unlike OSU, Bama, UGA, UM, etc. who have 15-17 thousand student sections, ND has a few thousand in theirs. I’m sorry but that makes a huge difference in the atmosphere/noise.
As a fan who has attended many games in South Bend, I’ve long said there are too many old fans taking up seats. That said, I don’t begrudge them, they pay for them but many just don’t cheer like fans do at other venues I’ve attended like OSU, Clemson, and UT.
I have been at games in south bend where older fans are literally telling other fans to sit down. I’ve seen it several times in fact and a few times I’ve witnessed yelling arguments about it. That’s a problem IMO, fans in attendance should be loud and engaged, that’s the point of home field advantage.