But in the NHL and the NBA, two things happen and they happen in both games. First of all, as played in the modern age, both sports depend hugely on defensive systems, on team defense. This stuff goes out the window when the game is being played by players who never play together. In the NBA all-star game, you can't take 5 guys at random from 5 different teams, and expect them to rotate smoothly on defense. This applies, although probably not quite as much, in the NHL - where certainly every club also has a defensive system that they attempt to practise.
In addition, in both the NHL and the NBA, an "exhibition-game" mentality is in place. Which in these cases, means we're going to have a non-contact game. No hard fouls, no smearing someone up against the boards or giving them a two-hander in front of the net. This is why you get NBA all-star games where the losing team might score 150 points, and NHL all-star games where the losing team might score 8 goals. It doesn't seem at all like a regular game, let alone a well-played one, let alone one involving the best players in the league. It looks like a pick-up game.
Baseball doesn't have these problems. There are aspects of team defense to baseball, but it's not that complicated. Teams pretty much figured out how to relay throws from the outfield in the 1880s. Middle infielders turning a double play involves a pretty minimal level of team work. Most of what we know as defense in baseball takes place on the pitcher's mound; the next most important item is an individual player's ability to react quickly and properly to a ball put in play. These guys are all members of the same team, but what they do at specific moments often does not at all require what we generally think of as "team work."
Finally, baseball is a non-contact game most of the time anyway. There are really only three opportunities in the game for contact and collision: 1) a fielder making contact with some part of the stadium, like an outfield wall: 2) a thrown baseball making contact with the hitter; 3) a baserunner making contact with a fielder. These really aren't large parts of the game, anyway. They do happen quite regularly in regular play, and sometimes they can be very significant. But we don't miss them when they're not around. Their absence doesn't distort the game, the way the lack of physical defense completely distorts a hockey game or a basketball game.
Everybody is just playing, and everybody is still competing. Everyone wants to show that they deserve to be there. The pitchers still want to get the hitters out, the hitters are still trying to get a hit, the fielders are still trying to make a play. And that's baseball. That's almost all there is to the game at any time.