I just wanted to share my thoughts because I feel there is a common misconception that you have a better chance of admission if you do everything or are “well-rounded”. Think about this…If you are well-rounded you are PRETTY GOOD at this and PRETTY GOOD at that (at best). Colleges especially schools like Harvard, Yale, MIT, Stanford, etc. DO NOT WANT “PRETTY GOOD”. They want an EXPERT, someone who is extremely good at what they do. That’s why I feel it is better to be “angular”. (Also, If you have your hand everything it might make it seem like your doing stuff just to beef up your application, which won’t please the admissions officers).
Anyways, sorry for the yelling lol. Feel free to share your thoughts too 
I think it’s somewhere in between the two. Just because you are a math genius doesn’t mean you can fail history.
Someone please correct me if I’m wrong, but I also feel like you could make an argument that it is not so much about being excellent in one subject as it is showing commitment, involvement, and leadership and having quality of activities over quantity (which usually leads to being ‘angular’, but not necessarily) at least for schools like Harvard. I could very well be wrong though.
For schools like MIT and CalTech, I do agree with you and think you do have to be ‘angular’ in STEM, but without sacrificing your other subjects of course.
@Madeline25 Yes thank you for adding that. My comment was more directed toward extracurriculars but you’re completely right.
Colleges want a well rounded class, made of angular students with no deficiency :+)