My math teacher one year made a rule that if you skipped more than 3 problems on the homework you got a zero on it. This was because she was assigning 80-100 problems a night and I had only been completing just doing enough to get a passing grade because I didn't have an hour to spend just on math every night.
I wrote my first AP English thesis in high school on this exact issue: students being assigned too much homework and the detriment it caused them. I don't remember the source, but an academic paper from around 2010 (I wrote the paper in like 2012) talked about how assigning more than 5-10 math problems per night could cause way more harm than good.
Not only was it incredibly time consuming for people who likely had sports/music/jobs/family obligations/etc, but it reinforced incorrect learning habits. Basically, if you were given 100 math problems, but didn't understand how to solve them correctly, you'd just be reinforcing your mistake 100 times. Add in the fact I never had a teacher who would spend an entire class going over all 100 of them, and kids were basically learning the wrong way every night. Plus, at least in my experience, the assignments were turned in and then the class moved on to the next lesson, and by the time you were given the graded assignment back, you were already 3+ lessons ahead, still learning everything wrong because the foundation was built on sand, not stone.
Yea, I was always good at math but shit like that made me hate it. Like you said I either understood the concept or I didn't. Having a higher volume of problems wasn't going to help. The funny thing was, later on in high school, my english teacher gave me a list of all the assignments we would have that semester with how many points they were worth so I went through and figured out what I would be a able to skip (pretty much all the stuff that I'd have to get in front of the class for) and still pass. She did not give a shit about it other than initially being concerned that I was failing really hard for a while because most of what I skipped was at the beginning. I told her what I was doing and she was just like "... well ok if that's what you want to do...". I
Had a similar issue with a science teacher, we had to copy down several pages of words and their definitions every single night. Made me hate science when I'd normally love it. I just refused to do it and failed the class. Explained to my parents why I failed and they were shockingly understandable about it.