In various subjects, particularly abstract mathematics, I had to grind heavily in order to keep up with the class. I attended every office hours and pattern matched heavily, studying into the wee hours. (I had tried your method and failed in previous semesters).
Other subjects I had no problem. Low-level operating systems, writing, literary deconstruction, chemistry, foreign languages, statistics: I had no issues studying a reasonable amount and having a good work-life balance.
Eventually I realized that I was never grokking things with mathematics beyond a certain point. I was in office hours with the professor, asking how I could generalize the concept to a new problem. He said "just use your critical thinking skills! That's what employers are looking for." I truly didn't have the ingenuity to do it. I really wanted to be good at it, but I knew I never would be.
I think you are forgetting about the areas in your life that you don't excel at, that you couldn't be good at no matter how hard you tried. Some people genuinely have to grind at some things in order to succeed. For me, it allowed me to realize that no matter how beneficial it would be to have a Math minor, it wasn't going to happen. I spent that time pursuing coursework I would benefit more from.
Grinding will always fail with abstract mathematics because it distracts you from divergent thinking and spontaneous insights. The problem is that university courses are on a fixed schedule so people that need more time than allotted for this kind of study are not accommodated, which pushes a lot of people away from mathematics who could otherwise contribute.
That said, I tutor mathematics and I hear all day long "I can't do this" and it has never once been true. For the people I help it is usually a matter of finding how they learn best (visual, verbal, hands on...) and/or finding an appropriate metaphor. And yes, even despite this, they often struggle; but genuine struggle is a good reason to put in more hours. I don't dispute that.
Your prof's answer is the kind of answer that disgusts me. It's not teaching. In mathematics it is exceptionally questionable, because it is tantamount to expecting you to derive the whole of mathematics by yourself.
That's the introvert's version of "just be yourself, you're overcomplicating it" -- i.e. just draw on innate skills that I have without realizing and you don't.
I have a gift of getting good grades. I know what things will be on the test, I know how to answer questions so that I leave enough wiggle room to avoid exposing ignorance on a topic, and I know how to structure an answer to get partial credit if I really don't know how to answer a question. My GPA in my first undergraduate class was essentially all A+s (curse you intro to the philosophy of language!).
For my second undergraduate degree, I just flat out rejected that approach. I exposed my ignorance where possible (and typically as early as possible rather than on the final exam). What was surprising was how little impact this had on my grades. Some, but not much, and I learned a lot more. Now I try to pass that on to my kids, but the structure of school is such that everything in that system is oriented towards the wrong goal.
Really pushes me in the direction of homeschooling, I have to say.
For me, saying "I don't know" was more of a social fear than an academic one. I thought people only liked me for my performance. But, like you, I learned that saying it didn't really affect the outcomes I thought it would, but it did result in learning a ton more. And I think, socially, it actually helped, because it humanized me to people who just saw me as "that super smart guy who gets good grades". I was no longer a machine they could not compete with, but a companion in the same struggle.
It's also much less exhausting just being true all the time, rather than trying to achieve some arbitrary educational or social metric.
> You're point about ...
Now I have to think about a grad school because it's pretty much required for my field of engineering. I'm not sure if any grad school would be interested in my pitiful grades from back then.
Likely to be true for many people. I remember my uncle, who was a prof. in the US, bemoaning the fact (and this was way back) that some of his students used to come and ask him "What do I need to do to get an A?" His point being, of course, that those students did not have a genuine interest in the subject for its own sake (which tends to lead to better outcomes anyway).
For good or bad, academic performance is measured with GPA, so you should not be surprised to see people optimizing for this measurement. You can't measure "interest in the subject" and even if you could, you could not judge teacher and/or student performance based on it, so instead we have GPA.
[1] One exception was organic chemistry in high school. Never could get my head around it, though I did fine in inorganic. I think it had to do at least partly with the fact that in organic, you have to memorize much more (e.g. molecules and their transitions - hardly remember much now), whereas in inorganic, you have to use logic and deduction and problem-solving skills more.
Meanwhile I never specifically study for a test. I've just studied regularly every day, thought about these things regularly, let my subconscious do some heavy lifting, and built associations in my brain that help me derive equations or fill in gaps if needed. For my effort, I've got a ~3.9 GPA and all kinds of free time for dating, exercise, hobbies, and teaching myself useful skills in my field that university isn't teaching me.
I think the core problem for most people is that they are attached to the wrong outcome. Their goal is the high GPA. My goal is grokking material and making myself useful; high GPA is almost a given (and frankly redundant) after that, and the only difference between my 3.9 and a 4.0 is the tolerance for BS and busywork... and about a gazillion extra hours of work.
It is, of course, understandable, because people think High GPA -> Good Grad School -> $$$$. But I suspect, and your story confirms, that "Reasonably High GPA" + "An Actualized Human Being Who Is Not a Robot"[0] -> Good Grad School -> Richer Life + $$$$.
[0] - Not trying to denigrate those who take the other path, but I see them miss out on a lot of life and ultimately not be as developed and awesome as they could be. I'm saying these things not just about random strangers, but also about people I know and love. They've optimized primarily for passing tests.