As has been said- private, it's a commish/owners issue. If they did their job (starting at the top with commish), they'd fill quickly, and be a desirable place to be. Public- I blame the owners in that world. Most of the public worlds that have large amount of holes have a large amount of turnover- which keeps the cycle going. But why did it get there? Were bad trades being ignored? Were tanking/inactive owners not being recruited to be replaced? If you have 10 LT owners in a public league and they take turns finding quick replacements, those bad teams aren't as undesirable, and you fill quicker. Not saying that's their job, just saying they could help the league they're in, and it would move along quicker.
My blame to WIS- the fact that there isn't some automated system in place to advertise and fill inactive teams mid-season and to replace owners under the tanking line. (What I envision is a page very similar to the open worlds signup page, where it tells you how may owners are available to replace, and you just click your way in like buying a new team. Maybe a limit per week or something, but I would love to see it). If there was a page I could go to right now, and quickly replace inactive/tanking owners in public worlds alone, it would keep those worlds better, and give newbie type owners more chances to learn for free.