Eh, there's kind of a precedent for this thing, in every other edition that includes feats. Just like a character with Strength 16 isn't really that strong, because the guy with Strength 20 is obviously stronger, the benchmark for comparison is someone who has everything synergized.
It was kind of the point of 5E, to reduce synergy. It was supposed to be that all you needed was a good stat, and proficiency in something, and you'd be good enough. One of the marks against feats is that it raises the expectations for everyone. If you're not using feats, then the strong fighter with the greatsword is all you need to fulfill the concept, and you're free to spend your other stat boosts on Dex or Wisdom or whatever. If you're using feats, then you're not "good" with a greatsword unless you've also spent the feat on it, because the benchmark for comparison has changed.