That may be so but the OP says he has only average grades and thus he's clearly not suited to any of those options.
I have three personal success stories that prove that's untrue.
The first is a Polish boy I met on the day that Poland joined the EU. We met at a party, and he impressed me with his unusually developed cultural literacy. He had dropped out of school for one year because of emotional problems after his mother had died, and was struggling in his next to last year at a special school for adults who go back for their GEDs. I decided that he was university material, and prepped him for his matura, in which he got all 5's (straight A's). He got accepted to Toruń to study Russian and English, but lasted only one semester. He showed up at my apartment totally defeated, but I told him that he was going to give it another try, and that he would move in with me so I could prep him better. He got accepted at Wrocław to study Bohemystyka (Czech), and I moved there with him. At the end of the first semester, he called me to tell me that he had gotten a 5 on his final exam, and all the other kids in the program had done substantially worse. AND the professors had given him the exam for second-year students, while the other students had gotten the exam for first-year students. He went on to finish his masters. At the end of his defense, the professors tallied up the points and saw that he had technically scored only a 4.5, but they petitioned the rector to give him a 5.
The second was a last-year less-than-average gymnasium student whose parents sent him to me because, even though they thought he was a bit slow, they hoped that he would get into the English IB program. Within fifteen minutes of meeting him, I realized that he was not only not slow at all, but one of the rare true geniuses that I have met in my life, and that's saying a lot. It soon became apparent that he was mathematically gifted, soon surpassing my ability to tutor him, and then the ability of a PhD mathematician from the university. He went on to complete a masters in financial mathematics at the London School of Economics. He was also gifted in philosophy, and his knowledge of English literature is formidable. His English is also formidable, and he speaks with a perfect American accent, courtesy of yours truly.
The third was a second-year high school student who had basically failed his first year of Liceum and was sent to a private high school, where he was not faring well until I got my hands on him. His third year was spent at a GED school. I basically brainwashed him into loving math and science, which was a challenge because I had to start at ground zero. He was a pretty good tennis player, and I got him, and his twin sister, full-ride scholarships to study at good universities in the US. Both are in their third year, now, she in psychology at Duquesne, and he in civil and environmental engineering at Detroit mercy, where he is a voracious networker.
My other students were doing well in school when I first met them, but these three show that practically every student has the capability to perform far above their level if they are properly mentored. It takes a lot of time, and love. And even personal sacrifice (I supported and even lived with the student studying Czech throughout his studies, and currently half of my earnings here in the States go toward supporting another one of my Polish students who is studying international relations in London).
And, if you are thinking why I support his choice of international relations, it's because he has abundant natural talent and drive for that field. He just got accepted into a very prestigious masters program at Kings, and I can easily envision him becoming a high-ranking diplomat one day. He also has the right family connections to do so, both in Poland and the US. (Actually, I still pester him to beef up his math and science). He's become interested in psychedelic drugs and drug policy, and has become a well-established junior member of the pertinent academic societies, in the UK and the EU. He is, of course, a super networker, as well. He'll walk into any job that strikes his fancy when he finishes.
I believe that all young people have incredible potential that just needs to be cultivated and developed. Potential that even they and their parents are not aware of. And that there is a great, untapped supply of academics like me who can mentor them. With the right mentor, I believe the OP can indeed finish a math-intensive major like my engineering student is doing. I don't believe that there are people of normal intelligence that do not have the ability to study math, science or languages. And also that most geniuses remain undetected because the school system is geared toward average students, and anything not fitting the average gets classified as below average.