Counterpoint: I can identify which part of the UI most of those come from. This level of variety between various UI functions is actually good. I don’t want the interface tabs or the settings tabs to be confused with tabs in the store, even though they are all tabs. I don’t want buttons to all look the same, especially not the huge purchase button. But even accepting that as an outlier I want some buttons to be clearly part of the steam UI and some as part of the site page I am on, so I don’t get confused.
Counterpoint: I can identify which part of the UI most of those come from. This level of variety between various UI functions is actually good. I don’t want the interface tabs or the settings tabs to be confused with tabs in the store, even though they are all tabs. I don’t want buttons to all look the same, especially not the huge purchase button. But even accepting that as an outlier I want some buttons to be clearly part of the steam UI and some as part of the site page I am on, so I don’t get confused.
probably boosts user performance for users who have more experience like you but slightly hinders new users who haven’t got the hang of it yet
if steam prioritizing retention of growing userbase is one of its goals, it’s not a bad strategy in my opinion