Reminds me of an old adage I heard in high school: If you take the frogs out of the environment, you don't have the same environment minus frogs, you have an entirely new ecosystem.
The sad thing with this "keystone species" concept is that people see it as "oh but this weird insect that's about to go extinct in south-east asia is not a keystone species, so whatever."
In the short term it's reducing the diversity of the ecosystem, yes. And the effect of that tends to pull in quite a bunch of effects that contribute to that effect even more. Only in the long run will there be more diversity again. But by that time we'll all sit in Musk Kingdom on Mars with oxygen masks and radiation suits and legends of ancestors who used to know what a summer breeze at a lake felt like, cause we succeeded to colonize another planet and that was totally worth it!!!11
