There's a lot of interesting discussions on r/science but like the rest of reddit it's such an echo chamber that you end up with bizarre one-sided arguments that discourage all opposing views.

Broadly appealing subs like that should be the last subs you cite if your goal is to provide evidince that Reddit isn't lowest common denominator trash.

Even in fairly niche subs I find that "surface level" content quality dominates and nuanced takes are frequently unpopular which is basically a recipe for anyone who knows anything to leave. I find the best subs are satire subs because having to know enough about something to be able to satirize it weeds out all the people who create and perpetuate surface level content. I assume there are some super niche subs that are similar.