Audio slider controls SYSTEM audio. WHY?

Why is it even necessary to have the volume output slider control my entire device audio, instead of JUST the app? I want to turn down zoom ONLY to not have my ear drums blasted, since your app is so poor to use!

I try to use volume mixer to change the audio as well, but it's never permanent, and every zoom meeting is a new meeting where my ears are damaged by the loud audio. I already suffer from enough hearing damage.

Is there some misunderstanding for how this app works, because I'm tired of opening volume mixer every meeting. If there isn't, PLEASE fix this already.