No, some people are so stupid that they will never be able to do tasks much more complicated than e.g. sweeping the floor. You are trying to conjure a vision of the world that is comfortable to believe, but that vision does not reflect reality.

Assuming you have your mental faculties completely in check, I don't see why anyone couldn't have been the text Tiger woods when born in the correct environment to be honest. Tiger woods isn't the strongest person in the world, he isn't the most flexible person in the world, and he isn't the smartest person in the world, but compared to others he has probably tens of thousands of hours on them practicing the correct things, and that is what makes him elite rather than anything about his physical body or intelligence. He actually has a pretty frail body and over his various controversies has shown remarkably poor judgement at times. You find anyone who has spent this sort of time on any activity and they have serious prowess, whether it be putting a golf ball or playing violin or running down an antelope.

I'm not sure the assumption that the comment above you is somewhat delusional is not necessarily reasonable here. I do think its that people are interpreting "everyone" differently.

To me, 'everyone' does not mean literally every person but rather the vast majority. Whether this number is 95% or 90% is going to be interpreted differently. I think nearly all of us can agree that as intelligence falls on a bell curve there will always be those unfortunate enough to not be able to do certain tasks. However the nature of the bell curve does mean that around 90% of people are above ~80 IQ.

If you take someone with an IQ of 100 and train them for a decade I think it's still very unlikely that they would become an elite chess player/musician/etc.

I see intelligence mostly as your rate of learning. That means you're competing with people who will get better faster than you. The only way to beat that is to outwork them, but there are only so many hours in the day.

Your understanding is the correct understanding Alice! But I think you're assuming most people understand it as you do, and that's not correct. Most people haven't learned to think with probabilities or distributions, and I would just downgrade that to "many" even here. I think many of the people commenting and reading here actually believe that one could e.g. teach calculus to everyone, it's just a failing in our efforts.

The Polgara sisters are evidence for this.