I wonder if mass extinctions are necessarily bad things.
They aren't necessarily good either. Yes, they have provided key moments that changed the course of evolution. But who is say interesting things would not have happened without them? We simply don't know. Those are alternate realities that we can only speculate about.
And as for the extinction event we are causing being "natural", the fundamental difference is that it is, or at one point was, preventable. Conscious beings taking conscious actions allowed species, genii, and soon whole families to become extinct. The asteroid, the Permian volcanoes, and so one were natural outcomes of natural processes, not planned, conscious actions that could have stopped.themselves.
That said, if this is a mass extinction event, we as a species are toast. Mammals as a clade might be, too. Fact is, the dominant group has never been the survivors of a mass extinction. While dinosaurs survived in the form of birds, non-avian dinosaurs were the dominant ones and they are gone.
Maybe there will be a new dominant species or clade or whatever, but given how long it took for sentience to evolve, there probably won't be another like us for a very long time. Whether that is a good or bad thing is, again, speculation.
My contention for a long time has been that environmentalism is not about saving the world. It can take care of itself absent our messing around. It is about saving ourselves. And so far, I am not hopeful.
And let's not forget that one solution to the Fermi Paradox is that civilizations generally die out before going interstellar.
