I've read some graded readers in Korean but my overall reading comprehension has been stagnant for years, and I've never properly finished a real book. I made some progress on the 나 혼자만 레벨업 web novel and Hello Jadoo tv show, but I've not stuck to them enough to keep 'leveling up'. Essentially my problem has always been insufficient ongoing exposure to new words to make them stick. I don't read fast enough or long enough to trigger frequent exposures.
If immersion in native content isn't triggering the repetitions I need, then SRS and engineered learner content seems like the obvious path to try.
My new/current/future plan is to build up to the web novel through the natively levels by reading graded readers while sentence mining to get 100% coverage as I go. I think using the natively levels and tracking might make things a bit more methodical so that I can finally build a snowball that doesn't break apart. And reading at or below my level is so far giving me better i+1 sentences to easily absorb new words.