One subtle issue in learning words from reading is that with languages like English where there's ambiguity in how to pronounce a given spelling, sometimes you might not guess the correct pronunciation for words you learned. This isn't specific to learning non-native languages either; growing up I read a lot and learned most of my advanced vocabulary that way, so as a teenager I would often find out that I didn't pronounce a word correctly because I had only ever seen it written down before.
There's a quote I've come across before, never make fun of someone mispronouncing a word in English, because it's a sign they are a reader.
I was in my 30s when I learned "ennui" was pronounced "on wee" rather than N-U-I. I did not know it was from French. No shame. I never spoke the word aloud, but used it in writing. A teenager I knew was studying for a vocab test and had to learn the word, and I overheard him flash carding. Pronounced it "on-wee" and my brain exploded.