Saw this comment about #gnome4 #adwaita theme flat design that rings true:

> changing buttons to be plain icons means removing crucially important contrast between elements and weakening visual cues to the user that things are clickable. In effect it makes it harder for the brain to “parse” the interface the person is looking at and leads to users having a harder time navigating the interface

(Personally, I think icon-only buttons are a necessary evil for mobile)

https://blogs.gnome.org/aday/2021/10/12/platform-design-goings-on/#comment-23856