They would have lost syndication rights if the show has archs. Syndication is extremely important to any network. UPN being a brand new network couldn't afford to loose that substantial amount of cash.Part of Ron's grudge probably comes from the fact that he saw a ton of potential in Voyager, and felt TPTB at the time were squandering it. He's not entirely wrong. Story arcs with long term consequences should have been mandatory given Voyager's situation.
DS9 wasn't the fan favorite until after the show was completed. UPN couldn't wait until the show was written, said & done for fans to come to love it, they needed results right away.
Ron Moore just wants to be his own boss and not have to answer to anyone above him.