That might work for established artists like Pearl Jam, but consider Pearl Jam in the early 90s.
They made enough money to retire off their first album. Under the kickstarter model, they wouldn't have been able to earn anywhere near that much money as no one had heard of them outside of Seattle before their first album release.
Was making enough to retire their goal? Making enough to keep making music as much as they can seems like enough for a lot of musicians. If it could reach that level, I think it would be a "success".
They made enough money to retire off their first album. Under the kickstarter model, they wouldn't have been able to earn anywhere near that much money as no one had heard of them outside of Seattle before their first album release.