I understand, but excluding preference for our own existence -- and that of species we find pleasing or familiar -- wouldn't preventing a mass extinction event

I understand, but excluding preference for our own existence -- and that of species we find pleasing or familiar -- wouldn't preventing a mass extinction event prevent the rise of new species? Every mass extinction so far became an opportunity for new species to rise and spread, of course to the detriment of many others. So why would you consider us to be "helping", if we exclude anthropocentric arguments? Maybe we are actually doing harm by preventing the rise of some new interesting species.