My first concern was that steps needed to be taken to prevent further undermining of the support piers. They seemed to have enough bearing to support a vertical load as long as no more erosion took place.
Then I realized that in their current condition they no longer resist a lateral load and the only resistance to a lateral load is the deck connection to the home and to a fire pit built into the deck (#5). The framing included no lateral bracing. At that point I changed the recommendation from correction by a qualified contractor to evaluation by a structural engineer.
It felt solid with just a few of us on it, but get 30 people dancing in unison… and I mean heavy-beat rock n’ roll, not slow dancing to Nat King Cole… and bad things could happen very quickly.