This may fall on deaf ears, but I'll give it a go anyway.
Just because one finds manually-computing equations difficult does not make one dumb.
I was a straight-A student in math right up to Algebra II, after which point my grades suffered -- I went on to get A's again in geometry, trig, and later stats but later again struggled with my advanced Calc classes and struggled terribly in Linear Algebra, to the point where I ended up leaving college after 3.5 years in a computer science program with a 3.0 GPA (only not a 4.0 because my math grades were mediocre at best)
I excelled in all my other courses, and ultimately found a satisfying career as a software developer despite my lack of a degree. I don't regret any of my years in school, but I don't doubt that it would have been an even more rewarding experience if it were possible to tailor the curriculum to my specific interests and talents.
For the most part my difficulties in math all stemmed from my inability to accurately do the algebra *quickly* -- it wasn't that I couldn't do it at all, and in fact I had many epiphanies in math classes while absorbing the concepts being presented -- especially in Linear Algebra -- some of which I find quite useful to this day. I'm sure I'm not alone in this. I'm quite sure I could have done better in most, if not all of my math courses simply given twice as much time to complete my exams -- granted I had the motivation that I actually wanted to learn all that stuff. If I had wanted to become an actor or lawyer, for example, I'm sure I wouldn't have bothered to even try.
It's possible that I may have had a different experience all the way through if I had had a different Algebra II teacher (she wasn't bad, but I sometimes had a rough time following her methods) though I think it's more of a thing with the way my brain works.
Am I dumb? I don't think so. I'm a good visual designer, as well as a competent programmer in any language I need to use. I pick up human languages fairly easily, am a decent cook, and have a knack with most machines. I do my own electrical and plumbing work (to code), and am a passable carpenter, welder and machinist.
My personal experiences aside, it's possible to be a frigging *genius* in one field, and yet unable to find even basic competence in another. I'm sure there are many great composers and choreographers (for instance) considered by not only their peers, but by the world at large to be at the top of their professions, that can't solve complex equations. Does that make them dumb too?
You're also discounting social intelligence, and the myriad other forms of intelligence that humans (and some other animals) can possess.
Humans tend to specialize, and even "generalists" like myself are a kind of specialist in a way. The ability to just pick things up and learn practical things quickly is (in my opinion) a form of intelligence. Granted I may be biased, since I seem to have that one.
We (as a society) need to recognize each other's value: simply as fellow human beings, as well as the specific talents we each possess, particularly when they don't conform to the "curricula" that happen to be in vogue at any moment. The talents to care for the sick and elderly, dance exquisitely or counsel the mentally ill (for just a few examples) are all vitally needed -- and to simply label people who have those important skills "dumb" because they can't reach a particular watermark in an academic discipline that they may, or may not actually need, does them, as well as the world at large a huge disservice.