Don't get me wrong. I also thought Vanguard was amazing. However, I found that it did too much tying to TOS. Pick one element and build on that. DS9 took the Cardassian/Bajor situation that had been set up on TNG and told a great story that didn't rely on tons of crossovers and prior TNG story lines. They certainly used the occasional element from prior series and even did a crossover episode but they were very much the exception rather than the rule. By the end, Vanguard felt like it was mostly set-up to me. But the ride to the end had many, many excellent stories. At it's height it was the best Trek series, bar none.