In my opinion, lecture is not the proper vehicle for providing direct answers or application of formulae – the kinds of things that you'd find in the textbook, and thus a "regurgitation"; rather, this would best be achieved at some recitation or office hours with TAs (who are often extremely helpful in helping students understand course content!). Rather, the purpose of the lecture sessions is to explore important ideas in the subject and link them to profound implications for society, institutions (such as public policy, law, and financial systems), technology, and the natural universe, as well as the human condition. In this way, you may find yourself mired in quite some degree of abstraction, formal proofs, and derivations of central theories, which can seem disorienting without tangible practice; this is normal. Everything may seem strangely uncorrelated or not coalescing correctly in your mind upon first sight, but most of the time there are relevant and meaningful connections that you'll discover after, say, repeated exposure from various places (the lecture, the textbook, the academic literature, slides from other university programs).
As an aside, why should we spend significant moneys or get into unreasonable levels of un-bankruptcy-able debt to hear a lecturer spout the same thing as the textbook? JUST BUY THE TEXTBOOK INSTEAD AND CALL IT A DAY, THEN! (unless your goal is to enter industry, that is, in which case the piece of paper that says you know some such stuff may be prized).
Notably, courses usually indicate how many hours you should be spending outside of lecture by the number of "units" or "course credits" in which they are advertised. Of course, this is only a suggestion. These hours should be spent, ideally, in optimized fashion reinforcing the key takeaways from lecture, and then identifying connections between these and the detailed computations and material particulars contained within the texts. This is the stage in which you should be playing around by making hypothesis about what the fundamental theorems say the output should be given certain use cases and input conditions, including edge cases or otherwise interesting or unusual scenarios, and conducting the analysis to verify that the results match your expectation. If not, what was your faulty reasoning? This practice will prepare you for any upcoming assignment.
As a personal test, determine if you can finish an assignment with little to no notes or other references. After seeing the concept multiple times at this point, it should be easier to compute answers or solve related proofs. It may take time and thought, but shouldn't require the textbook if you understand it "to a reasonable level". You don't need to know everything deeply yet, but rather a moderate comprehension, which is enough at this stage.
In going one step further than expected by the professor, you may locate the most influential publications in the field and other primary source content and read those to achieve an even deeper contextual understanding of the field. They are often free and accessible when using your .edu account, or found in the library. This isn't required, if you have time constraints, but it demonstrates initiative and you learn directly from the originators of the theories in question.
Lastly, there's often a project component, typically towards the end. This is an opportunity for you to see the content in application, and it might be the most important part, allowing you to bring together everything you've learned and use it to build something or conduct an experiment, expressing your creativity in the process. This is when I found that I learned the most, as long as I put forward significant time; if you half-ass it you won't learn anything additional, but if you focus, you may actually come away from the course realizing that you understand the core of that area much more than how well you "know" or "learned" information from a textbook for your previous classes. You'll also find that you have a new-found appreciation for the topic, beyond your initial interest during the first lecture.