So what exactly are they supposed to do, then? If they are supposed to "grow the game", I would argue that the best way to do that would be to play very well on a world stage. This would require them to actually have more time to practice together, but they make do so that they don't spend too much time away from their pro teams, which they are also required to play for while they "grow the game". Oh, but they don't make enough money to just play in the WNBA (some do, obviously, but it's nowhere near what they make overseas) so they have to supplement that with European or Asian teams in the offseason.
And the majority of players choose to play in the WNBA to do just that..."grow the game". They could easily play only overseas, take the summer off and make plenty of money. But they kill themselves to play all year round to make the WNBA competitive and compelling for an American audience, and then take three weeks to go play in a major tournament, where they have to not only win but "not win ugly", and then come back and jump right back into league play.
Soooo again, I don't see a problem with them taking a few weeks off. In the long run, it does help grow the game by seeing the best players at the Olympics, and at their physical peaks.