It's pretty easy for a childless adult who works downtown and can afford to live in one of the more central neighborhoods of Seattle, and still workable in certain neighborhoods further out that have walkable amenities and good transit connections. If you're willing and able to get occasional rental cars/ride shares then it's absolutely trivial.

It's not easy for a lot of other people though. Rent in those neighborhoods is too expensive for most, and while you can take kids around by transit or by bike (and I certainly encourage people to do that when it's convenient), you'd have to be a pretty dedicated urbanist to do that for all your trips.