Part of it is I don't think Bruce is the greatest live performer anymore. He was a true groundbreaker in the amount of energy and passion and time he put into his shows but that's not unique anymore.
I could see being amazed at his shows in the 70's and even 80's but what he does now is normal for most acts. I love his shows because I love his music but I never leave shaking my head thinking I saw something I hadn't seen before. So if you brought a new person to a Bruce show now, it wouldn't have the same impact.
My last 2 concerts were Queen and P!nk and I would imagine (if you were neutral about P!nk, Queen and Bruce), the Bruce show would have been the least impressive and impactful show out of the three.