The wood pillars in my pics are useless, gaps beneath all of them. I put the jacks in something like 25yrs ago, and there's been some settling over the years (especially with the 1.1 earthquake)--note in the first two pics blocks on the far side with no jack, so loose it had fallen down (now back in place, those are 'before' pics).
We priced having it done, trying to find someone who would just tighten the jacks. Both places wanted to replace everything with new piers and wood (and not that expensive), but then would not guarantee that the bit of bounciness in the floor would be fixed.

So I held my breath and did the readjusting myself, took about two hours, and another couple hours cleanup, laundry, and putting stuff away. And yeah, the wood posts should be removed and the same blocks+jacks put in there. That might be next year's project...
If you look at my pics, years ago I also wrestled big foam panels down there and onto the bottom of the floor--two layers, 8cm of insulation. When we moved in there was nothing.