How many fans or potential fans ask/tell themselves, "I'm not going to this game or this game solely because of the arena"? Probably very few, if any.
How many fans or potential fans ask/tell themselves, "I don't think I'll go to this game as it's just not "fun" or electric at the arena. I'll just watch it on TV".
Probably a great number. Attendance shows it.
No one is saying a new arena is the single magic bullet, but the atmosphere definitely can attract fans, even if the team is not good. Just look at the Thunder, after coming off back-to-back 50-loss seasons, and being below .500, still averaged 18K per game in 2022-23. The attendance at OU isn't just a PM issue- actual butts in the seats have been an issue for a while. Even when the team has been good, and regardless of the coach. It's just exacerbated the last couple of years. The arena environment makes a difference.
But a more appealing arena, environment, ease of access, entertainment value, etc. does drive attendance, which impacts revenue, which impacts NIL and so many other things.