I'm not sure what kind of defaults you would like to see. For instance I have this in my i3 config:
bindsym XF86AudioRaiseVolume exec --no-startup-id amixer sset 'Master' 2%+ bindsym XF86AudioLowerVolume exec --no-startup-id amixer sset 'Master' 2%-
but there's no guarantee that this would work everywhere depending on what's installed, I just know that it works in my case. It's easy enough to look up anyway ('linux change volume from terminal'), so users would just save 5 minutes if the default worked for them. I think the message is that i3 is not targeting the same people as Gnome, and it's fine. Different software for different needs and trade-offs.
MATE with i3 as its window manager is excellent. No compromises, neither gets in the other's way. I wrote how to set it up here: https://www.mattgreer.org/articles/mate-and-i3/
Re:I3: Improved Tiling Window Manager
by reportgunner on Thursday December 17, 2020 @07:34AM
(#25454995)
This. I just install debian with MATE, install i3 on top, clone i3 config file from my git repo and all setup is done. Sound works, brightness works, external displays work.
I have tried regolith, but I found it to have weird conflicts between i3 and gnome. It may be worth another look though.