The problem with most vocabulary lists is they feel disconnected from how you actually write. I spent years trying to memorize fancy words from apps, only to have them sound forced when I dropped them into a draft. A shift happened when I started keeping a 'stolen words' document. While reading, if a word stops me—not because I don’t know it, but because its use feels sharp or surprising—I jot down the sentence. Not just the word, the whole phrase. Then I practice writing three new sentences where that word wouldn't normally fit, trying to make it feel natural in a different context.
This method leans on seeing vocabulary as a toolkit for tone, not just ornament. Reading outside your genre is huge for this. A technical manual might have 'exogenous' or 'attenuate,' a noir novel 'crepuscular' or 'laconic.' The goal isn't to sound smarter, but to have more precise tools. A character doesn't just 'walk slowly'; they might 'amble' if relaxed, 'trudge' if weary, 'shamble' if injured. Having those options ready makes description less about searching for a word and more about choosing the right one from a mental shelf you've stocked yourself.