not everyone can reach 2000
IMO, the only real thing separating most 2000+ players from the sub-2000 players, is the 2000+ players have learned things that the lower players have not.
Teach the lower players the same things that the 2000+ players know, and they'll be right there with them. :)
You must know chess is not a game of purely knowledge. It's about performance. You can even learn new things and have your performance decrease as a result!
In an interview after becoming world champion, Carlsen commented that he still has many things he can learn, but it's not certain that he will be able to use the new knowledge to improve his results (to 2900 for example).
i think quite everyone can reach 2000. i improved my rating within the last two years from 1750 up to 1950 and surely will break through 2000 within the next months. what was the key? well i changed my openings completely from well known and sound to a bit crazy ones, but even more important i now stick to these openings and know them by heart. besides i am doing regurlarly tactic puzzles which of course also helps. another thing which is often underestimated is the clock-management (not only important in Blitz games). but even after all this i still see so many topics to work on. there are still opening lines i mishandle, middlegame, endgame and so on...
I think it needs to be said that, in order to truly "know" something in chess, you need to be able to apply it in game. From the practical point of view of discussing chess performance as correlating to chess "study", this is the only useful definition.

There is a limit to what one can change in this world. To be able to reach 2000 or not would have to be based on the individual level. First he has to believe he can do it. Second he has to have the right tools and mindset to do it. The list goes on and on. However if the individual does not believe he can do it, there is no point of telling him that anyone can reach 2000.

IMO, the only real thing separating most 2000+ players from the sub-2000 players, is the 2000+ players have learned things that the lower players have not.
Teach the lower players the same things that the 2000+ players know, and they'll be right there with them. :)
You must know chess is not a game of purely knowledge. It's about performance. You can even learn new things and have your performance decrease as a result!
In an interview after becoming world champion, Carlsen commented that he still has many things he can learn, but it's not certain that he will be able to use the new knowledge to improve his results (to 2900 for example).
Yeah isn't it interesting how it sometimes seems like top players can't improve (just their chess in general), or at least they often act like it? They just seem to act like the only thing at all that will improve their results is by seeing how to refute the novelty their opponent played in their game. Never anything general like, "I need to think things through better when making a plan," which is something we might say to ourselves.
And yet on the surface, you would think there must be such thinking errors that even the best players make, and can try to correct. Yet their rating stays the same. My only guess is that a 2800 player is so hard to outplay, that just knowing a few more patterns isn't going to be enough to increase your chances of beating him. In other words, surely the top players must learn things too, but I guess they don't learn enough to make a big difference in their results. I guess if you already have 500 million patterns memorized, what's another 10 or so really going to change? :)

But yeah, top players staying stagnant certainly seems to be more support that chess can largely be measured by patterns. The top players don't seem to improve because any patterns they learn will make up an extremely small percentage of their whole database of patterns. And teaching absolute beginners the opening principles will improve their skill right away because two or three patterns actually would make up a decent percentage of the beginner's knowledge base.