Again, if your point is that it takes more than a single player to be a good baseball team, I'm sure we all appreciate the new information. If your point is, trading Bryce Harper will magically improve the team from a non-playoff team to a playoff team, we can agree to disagree on any number of assumptions that go into that.
If your point is that playoff teams don't have superstars, I think you just don't have a good idea of what a "superstar" means.
Donaldson, Cespedes, Cain, Bryant, Heyward, McCutchen make up 6 of the top 12 hitters in baseball this year by WAR.
Kershaw, Arrieta, Price, Keuchel, Greinke, Cole, DeGrom, Lester make up 8 of the top 13 pitchers.
Of course top players do not guarantee anything, but it's silly to think they're meaningless.
Cain and Heyward don't come close to counting as superstars. Their value in WAR comes primarily from defense. No one is going to seriously consider them for an MVP. And like I said, Donaldson needed two other guys to hit 40 homers, the best shortstop in baseball, and David Price. McCutchen has been surrounded by quite a bit of talent in Kang, Cervelli, Marte, and Polanco, along with a top 3 pitching staff this season. Bryant isn't even the best hitter on his team, let along in baseball. And again, surrounded by talent. Actually, Rizzo was the cornerstone that the Cubs surrounded with talent like Bryant, Soler, Fowler, Schwarber, and Russell
Cespedes is the only one you might be able to make a case for, but again, the Mets surrounded him with good players and a top tier rotation. Cespedes on the Tigers had them below .500.
The Nationals are currently very good two relief pitchers (one of which is a closer), and about 4 good/very good players away from being a competitive team again. On top of that, they have to come up with a replacement for Werth (assuming Robinson can continue to be a quality hitter) who can cover for him when he misses 75 games next season.
They're no where near being a contender. They will not be next season. They MIGHT be in 2017, but it's doubtful. 2018 is the earliest that open can be reasonably open and that's IF Scherzer is a complete wash AND Giolito pans out AND Joe Ross hasn't torn his UCL AND Rendon hasn't suffered a career ending injury AND Turner has developed in to a decent hitter.
That's a lot of IF's to hang on to a player who you know is gone in three years and the only thing you're going to get out of him is a bunch of media stories and watching him get a couple MVP awards in your stadium. I would much prefer to punt it and build a truly dominant team three years from now.
Oh, and both of the current WS teams traded their supposed superstar and are in the WS because of those trades. The Royals traded Grienke to the Brewers for Alcides Escobar, Lorenzo Cain, Jeremy Jeffress, and Jake Odorizzi. Odorizzi was a key piece that brought Shields and Wade Davis to the Royals. That's three top players as a result of that trade.
Blue Jays traded Travis d'Arnaud and Noah Syndergaard for RA Dickey, who was coming off a Cy Young season. Worked out quite well for the Mets.