Personally I have no desire for a vow renewal. Of course, I was a bride who merely tolerated the most minimal wedding party while still satisfying the wishes of some very close family of DH and myself, so maybe I'm not the target audience.
I really have zero interest in attending the vow renewals of anybody else, particularly when they begin moving it into the realm of their wedding 2.0. There are very limited reasons I would ever consider attending such an event and I don't know anybody personally these reasons apply to, so I think I'm safe at the moment.
Anniversary party? Fine. Cannot wrap my brain around why long-term married couples need an audience viewing them repeating their vows. Seems too attention-seeking to me. If it makes the couple happy and their family & friends would enjoy attending, I hope everyone has a wonderful time. It's just a concept that's lost on me apparently.