Yeah, somehow there's always a lot of love for spaced repetition even though it doesn't help with comprehension. I believe re learning complicated topics is better than mugging up jargon.
“ Tod mach’s mir leicht, wenn du kommst vor deiner Zeit” reading it and understanding it is trivial. If you have to look up each word individually your comprehension will at best be enormously slowed. The same principle applies if what you’re reading is a chemical formula, a logical proof or a description of a historical event. Knowing the 200 or so most important events of the French Revolution by date with two sentences of explanation for context makes reading further on it enormously more productive.
If you're trying to learn the content of the book, the process of converting the information into flashcards entails engaging with the material, so that isn't skipped.
There are frequency lists of vocabulary words for languages: basically some words are used more frequently than others so memorizing the most common 1000-3000 words is enough to get very high comprehension rates for everyday conversation and reading.