When reddit switched to their new 'featureful and rich' ui they provided a way to access the old user interface which is much more utilitarian and flat.

I expect most experienced reddit users still use the old ui toggle. I expect new reddit users don't know it exists but would probably prefer it once they got over the 'change is bad hump'.

The fact that years later the old ui toggle is still present is a testament to how much the new richer ui failed for their power users.