Meddling is not fixing things we have broken. It's just altering things again but in a way we find intellectually pleasing. I don't think trying to bring back ecosystems to their previous state as inherent value. I don't value nature for nature sake generally speaking. That's a rich urban dweller idea of morality. My issue with the human impact on Earth - climate change and what it does to the biosphere - is that it's unsustainable and will have a massive impact on our way of life if nothing is done.
I don't really care about wild mammals in Europe outside of their rise being a signal that other things are doing better.
OK, I am sympathetic to the suspicion that reintroductions of European mammals might just be a highly-visible gesture aimed at our own enjoyment of "nature", rather than fixing of conserving the fundamentals. But plenty of people do value nature for the sake of nature - so there's just a values difference there.
But attention-grabbing species do make progress visible, and visible indicators of system health are very useful. Larger animals and apex predators can also have larger impacts on an ecosystem, both positive and negative. For example, it is often argued that the reintroduction of wolves to Scotland would reduce the artificially high population of red deer, which in turn would help the recovery of forests and the rich ecosystem they support.
That is an extreme case, but sometimes the best way to correct a human-caused error is a human-caused solution. Nature will always find an equilibrium, but probably not an equilibrium that works well for us unless we nudge it. Reintroducing sparrows is clearly better than accepting the natural equilibrium of "locusts are everywhere and we can't grow food anymore".