I don't see a reason why playing violin would be impossible given a couple hundred or thousand hours of deliberate practice.
Jumping higher than the WR is a straw man, since that goes for anything - there can only be one #1. However, people can increase their vertical leap substantially if they train things like olympic lifting and plyometric. See The Vertical Jump Development Bible for example programs on how 12-50 year olds can increase their vertical leap on the order of 20 inches.
I really tried the violin (I think it is one of the most beautiful instruments), and for more than 'a couple of hundred hours' and it did not work for me.
I'm not sure how to articulate the mismatch but I'm pretty good with other musical instruments but between the violin and me it never was love to play it, just endless frustration.
At least I can appreciate others that play it a bit better :)
This is not surprising, violin technique is deeply rooted in the body (especially bow technique) and is difficult to learn past adolescence because your body/brain cannot adapt as well in adulthood.
Source: I learned violin around age 13 after already reaching an "expert non-professional" level in piano, found it very challenging and eventually gave it up after seven years of study.
> Did others also think you didn't become better with practice?
Yes
As to your last two questions, I think there is some kind of reward/work element here that did not click for me. Normally if I put in a certain amount of time I expect to see a measurable progress. With the violin initially that progress was there and then at some point (relatively quickly) it reached a plateau and after that the amount of work for a given amount of progress seemed to me to be disproportional. It's the hardest instrument that I've ever really worked on trying to learn how to play it and maybe one day I'll overcome my resistance and I'll try again but I really feel like I've met some kind of personal Waterloo there and the chances of this happening are very slim.
(I actually tried twice already with much the same result, I'm not one to give up easily).
Jumping higher than the WR is a straw man, since that goes for anything - there can only be one #1. However, people can increase their vertical leap substantially if they train things like olympic lifting and plyometric. See The Vertical Jump Development Bible for example programs on how 12-50 year olds can increase their vertical leap on the order of 20 inches.