I think the OP is describing what I've typically seen in "be successful" books -- that it's a better investment to focus on making your strengths (in terms of TALENTS and NATURAL TRAITS) shine, rather than focusing on your weakest points and trying to make that a focal point of your success strategy.
The caveat is that if one or more of your weaknesses is REALLY bad, then it's worth investing enough to bring yourself up the bare minimal level with that ability or trait, simply so that it won't derail your strengths... but otherwise don't throw good money after bad.
The concept is typically aimed at management, where it's not a "solo sport" but you have the opportunity to surround yourself with people who excel in the areas that perhaps you stink at, so rather than trying to just not be weak, it's easier to give someone else a chance to invest in the area you are weak in. As a team, you thus have all the bases covered and everyone gets a chance to shine.
I generally agree with this. I mean, really, you're gonna go a lot farther by getting your strengths as honed as possible and bringing your big weaknesses up only to the minimal level needed, than you will investing that same energy into trying to make your weaknesses "average" rather than weaknesses. It takes a lot more energy to do that than to increase your strengths, because you're naturally inclined to use your strengths as well as invest in them, and you're inclined to not use your weaknesses nor invest in them.
Being a jack of all trades is cool; but as always, unless you find a niche for yourself that demands the ability to do everything to an average or a bit above average level, a specialist (few strengths, but highly honed) will outshine you EVERY time. If you want to have brain surgery, you don't go to a generalist; you go to a brain surgeon.