no, everyone knows it, but it's specific. dude above said なだらか is "very common", but even if it were the most common word in the language for that situation it'd still be kind of obscure to me because i don't talk about hills very often, and could get by without it even if i did. similarly, 咲く is common and has a pretty frequently used kanji and sounds like 桜 so is easy to remember, but hell if it's going to come up in my conversation very often.
all this is relative! i know a bunch of specific words related to things i'm interested in that most people of my level probably don't, and i'm sure it's the same for everyone. like, just because i see a bunch of complicated photography terms each time i turn on my camera doesn't mean they're not kind of obscure for people who don't care about photography.
at levels like my own, it's important to prioritise what you learn. you're evidently at the stage where everything is interesting and about as equally useful to know, but that's because there probably aren't any bigger holes that'd give more bang for their buck if they were filled.