We go through this every year, the issue isn't that we have a pathetic fanbase it's that people overestimate what the actual local fanbase is. There's a large portion people in the local and surrounding area who are casual at best fans. When SU is good they will discuss it and watch the game but they aren't attending a game in person really no matter what. There are tens of thousands of these people locally and the surrounding communities. It's not an issue of parking or cost or even the walk up the hill or being lazy, they just don't have any inclination to attend period. It's just not something that occurs to them as even an option. Sounds bizarre but trust me its 100% accurate.
Your point about the AMP is not apples to oranges and the main complaint I hear about the AMP is parking. SU attendance for a fball game dwarfs what the AMP gets that and they rarely sell out a 17K facility.
To get those true bandwagon fans who may attend SU has to win, it's always been that way. It's no coincidence the year after SU won 10 games season tickets exploded and when SU was undefeated after like 5/6 games a few years ago they had two near sellouts later on in the year.