if he is going alright with all the other topics as you say...then why tag a post with the title "hopeless teacher"? Or is he just a brilliant student when he understands something all by himself and blames teach when he doesn't understand something?
You know, maybe he's reached his intellectual limit?
He said he's alright with all the other topics, I'm not saying that based on nothing.
No such thing as reaching an ''Intellectual limit'' for someone who's still in year 12, a lot of other factors must be considered before jumping to this bald conclusion.
Mechanics is one of these topics that can look intimidating from the outside but even an average 2u student can do it, if taught properly and correctly. (No disrespect to 2u students). So if the OP feels comfortable with the other topics, then there is no need to consider dropping the subject. if however ( as I mentioned earlier) he happened to have ''more than 10 units and 4u is absolutely consuming his time [with no significant improvement] AND 4u happened to be his worst subject'' then the idea of dropping it may be considered, otherwise, It really sounds absurd to me.
Have a look at the 4u topics and let's look at it from the perspective of a student who's just there to get the mark (NOT referring the op, but just in general). You can reach an acceptable level in conics, polys, integration and even complex numbers by tedious practice. Mechanics and volumes require a bit of understanding and visualisation, however their questions are mostly predictable and can be mastered through practice, and probably the most challenging topic for a lot of students is harder 3u, it's probably the only topic that requires genuine interest in mathematics and a bit of abstract thinking. A 'hopeless teacher' can easily teach their class the first 4 topics that I mentioned and can rely almost completely on rote learning and example-based lessons but when it comes to the topics that require a bit of proper explanation, their incompetence -as an educator- becomes evident.
It's also possible that the student is currently not capable of coping with 4u but that doesn't mean it's because they reached their intellectual limit, it just means they lack the mathematical maturity to take on some of the abstract ideas that 4u has, and that's not what the OP talked about, he only mentioned that he struggles with mechanics because of the methods and teaching style that his teacher decided to adopt. Which means if someone who knows how to explain things well taught him, he most likely will have no issues with the topic anymore.
If perhaps the OP is actually really struggling with the majority of the topics in 4u and just cant seem to handle it anymore and cant find anyone to help him or any good resources, I might then see your point in advising him to consider dropping the subject.
but I have a test that involves mechanics before trials, so I guess I'm going to have to work hard to catch up through the coming weeks.