When you "destroy" an ecosystem, a new one will take its place. The remaining animals and plants will converge on a new balanced state.
The ecosystems we admire today are often that new balance after humans destroyed the natural one.
In almost all cases, when a collapsed ecosystem reaches homeostasis again, the result is a more fragile and less diverse balance than what was there previously.
Monocultures are a scary thing (I'm sure you've heard about how we had to completely switch banana varietals), and having resilient ecosystems is important. I think ATM the consensus is having an apex predator does actually help the stability of these sorts of ecosystems and leads to outcomes most would consider favorable (greater diversity, better density, closer to an equilibrium). Now, we could surely fix this problem by doing it ourselves (eg by subsidizing deer and rabbit hunting and venison), but wolves are probably cheaper.
There's no guarantee that this be a stable equilibrium.
If it doesn't stabilize, we get mass extinctions. We have had five large ones and are rapidly moving towards the sixth ones by all accounts.
The scientific consensus isn't that we're "moving towards" a mass extinction. It's that we're deep into one, and accelerating.
"Current extinction rates are estimated at 100 to 1,000 times higher than natural background extinction rates [13][14][15][16][17] and are accelerating."