The reason many 1Ls get crushed after grades come out is because they mistakenly carried the "hard work means good grades" mentality into law school. The bolded part of your post is me pointing out that you're making the same mistake. What I think you really need to do is change how you prepare for exams.
My advice to you
FOLLOW AT YOUR OWN RISK
I'm a fellow slow worker. When I prepared for midterms like everyone else, I got the same marks as everyone else. When I prepared for final exams like a slow worker, I beat the curve in 6/7 courses. The only course where I didn't beat the curve was also the only class I made the mistake of not doing the aforementioned.
Understand that you can't do all of the assigned work. It may take other people 1 hour to do a 30 page reading while it takes you 4 hours (I personally need to read every word on the page). Doing all of the assigned work is just not feasible for you because its not an efficient use of time. There is absolutely no shame in admitting this or accepting this. Doing all of the assigned work is just one of many different ways to prepare for the exam. You should let my exam grade determine whether your unique method of preparation is right or wrong.
Understand that doing all of the assigned work doesn't mean you shouldn't be doing any work or even less work, it just means you should be doing the work that helps you best prepare for the exam.
Doing the readings - Your main focus should be to make the most efficient use of your time (i.e. doing the type of work that helps you, as an individual, best prepare for the exam)
First, check the syllabus to understand the place of this reading in the class (you'd be surprised how many people overlook the value of the course syllabus). The question here is: what am I reading? What topic is this reading on? How many days will you be dealing with this topic? How many pages is it? Is the topic a standalone topic or one piece of a bigger topic? This will give you a rough idea of how much time and concern you should give to this topic and also generally primes you for the work you need to do.
Second, very briefly skim the reading while paying attention to the structure of the reading. Read the headings, intros, conclusions, etc. This will help you understand the skeleton of the reading.
Third, once you understand what you're reading (i.e. after completing the first two steps) your next question is: why am I reading this? Why has the professor assigned this reading? In other words, what does your professor want you, as a student, to get out of this reading for the purposes of their class? To answer these questions, look to course summaries/CANs from upper years who have taken the same course with the same professor.
Fourth, now you know what you're reading and why you're reading it. The question now here is: what does this reading say about that? If you're a person who's comfortable relying on a summary/CAN, then rely on your summaries/CANs to provide answer the answer to this question. If you're a person who's more comfortable doing the reading, then let the summaries/CANs create the signposts of what's important in the reading so you can focus on that and allocate your time effectively. For example, if you're dealing with the topic of sexual assault in 1L criminal law, then you're probably going to want to read all of Ewanchuk and only focus on the bare essentials in every other case (e.g. R v Chase - only matters because it tells us how to interpret the sexual nature element of the AR; R v Cuerrier - only matters because it tells us when fraud vitiates consent and what L'Heureux Dube and McLachlin say in their respective dissents, respectfully, doesn't matter for the strict purpose of your exam unless your professor cares about policy; R v Mabior - only matters because it tells us when non-disclosure of HIV status vitiates consent/constitutes fraud; R v JA - only matters because it tells us to how interpret consent and, respectfully, Fish's dissent doesn't matter unless your professor cares about policy; etc)
Lectures - The purpose of lectures isn't for the professor to spoon-feed you the material, for you to practice your skills as a typist and copy the lecture verbatim or for you to get your online Christmas shopping done. The purpose of the lecture is for the professor to:
Confirm to you that you're on the right track (i.e. you've done the aforementioned Reading stage correctly and understand what the topic is, why you're doing the reading, and that you know what you need to know)
Clarify anything in the readings and/or correct any mistakes/things missing from your understanding/notes or the summaries/CANs you've relied on
Provide you with their unique perspective/opinion/approach to the topic at hand. You're going to keep this in mind when writing your exam in order to cater to their beliefs, prejudices. For example, if you have a feminist professor, don't argue that sex work should be criminalized on an exam. Present both sides to the argument, and in one sentence say that you support it even if you don't. As a future lawyer, you're going to be arguing a lot of things you don't agree with or believe in for your own personal gain. Might as well start early
Give you any hints about the exam. Professors notice if/when the herd thins out during the school year and some times will be inclined to reward students for attending. There have been multiple times that I've gotten useful hints about exams from a professor simply for being present during a boring lecture in the middle of October
Exams - Exam-writing is a skill. Learn it.
Read books on how to develop the skill. My recommendation is "Law School Exams: A Guide to Better Grades" by Alex Schimel.
Create your own outline. In your 5 to 15 page outline, you should have every piece of the "what you need to know" part of each of your readings. There should be absolutely no superfluous bullshit, fluff or fat on your outline. You've literally condensed the entire course into those 5 to 15 pages. Your casebook, other peoples outlines/CANs, etc were all just tools for you to arrive at your own outline.
Learn your outline cold. I mean cold. This doesn't only mean just memorizing it. You should be able to open up ExamSoft and type out the blackletter law part of your future exam answer on demand and at near-lightning speed. The only class that I actually did this properly for was the one I finished at the top (and despite missing a major issue on the exam) and the other class that I did this, but sort of half-assed, I got an A- despite writing one paragraph for a question worth 33% question because I blanked out.
Once you've learned the outline cold, take a few old exam questions and do timed exams on ExamSoft. Your focus is to type out the blackletter law as you've been doing and then actually apply it to the facts. Review your answer by yourself, then with a professor (if you can reach them/they'll allow this) and finally compare against old exam answers. Many people will disagree with this but once you do a few of these timed exams, you'll start to notice repeating patterns in terms of the issues tested, answer structures, etc (there can only be so many and also many professors are creatures of habit).