I did some research in to this this year in the context of maybe trying to start a business to solve this - and this was the conclusion I came to. There’s lots of threads here on HN about it too. It’s a structural, market-wide issue where the primary service Ticketmaster provide is reputation laundering, and in return, large agents and promoters agree to continue to use Ticketmaster despite their reputation.
I don’t know what the solution is.