Not at all. In my experience, many people of mediocre intelligence but a background that has sufficient education think they're geniuses. The variability in intelligence achievable by tutoring vastly exceeds the difference in their intelligence vs. that of the average inner-city high school dropout without a disability.
> People have different working memory capacity
Multiple studies have shown how this is easy to train.
> different abilities to reason deductively
This is also very easy to train by example.
> I almost certainly would never be able to make a college basketball team let alone the NBA
Being able to do college algebra isn't equivalent to making the NBA, which means being in the top fraction of a percent in basketball ability. Being able to do college algebra is equivalent to being able to dribble.
Running ability is also easy to train, that doesn't mean everyone can run a marathon. Some people have flat feet or poorly proportioned limbs unsuited to long-term running. These aren't disabilities preventing them partaking in such activities, but nevertheless limits their potential.
> Being able to do college algebra is equivalent to being able to dribble.
No, it's being able to at least dunk. Again, a common skill but not one everyone can achieve.
Everybody without a disability can run a 5k. High schools used to require students to do a mile run to pass physical education.
> Some people have flat feet or poorly proportioned limbs unsuited to long-term running.
And some people have microencephaly. We're not talking about outliers. We're talking about the vast majority of people.
> No, it's being able to at least dunk.
Look, you're not special for being able to learn college algebra. Get over it. 95% of Koreans and Singaporeans can do it today, but this wasn't the case 60 years ago. It just requires a basic level of education.
No, you specifically said "people without a disability". Unless you're going to expand the meaning of "disability", various permutations within the range of "normal" physical characteristics will impose different limits on athletic abilities, and analogously, the range of cognitive qualities (memory, focus, spatial reasoning, etc.) will do the same for cognitive tasks.
The fact that these qualities can be improved via training doesn't change the basic fact that those limits will be quite different for different people, even within the normal range. We can quibble all day about whether college algebra falls under that category, but this basic fact won't change.
And that range is smaller than the difference between your ability to perform cognitive tasks and the average high school dropout's ability to perform those tasks. Education makes a much larger difference.
Your study is about the effect of an extra year of badly done education on people who drop out of school, which is worth 1 IQ point. That same study shows that the effect of mediocre education on people who don't drop out of school is an increase of 5 IQ points.
I think that's a stretch, unless you expand the meaning of "intellectual disability". I would agree that considerably more people can succeed than currently do because effort can make up for a lot, but that's a different claim.
People have different working memory capacity, different abilities to reason deductively and considerably more differences on various other metrics of cognitive performance. There are as many dimensions to cognitive performance as there are ways to measure athletic performance, and people fall on very different parts of this spectrum.
With significant effort over time, I can make up for athletic deficiencies and become a pretty good basketball player, but being 5'9" I almost certainly would never be able to make a college basketball team let alone the NBA. I'm not sure why this same logic applied to cognitive abilities is so controversial.