While that's true, if you don't have a proper transit network, it's a real problem. And many cities aren't in a position to build a proper transit network at the drop of a hat. Don't get me wrong, I wish they did or could efficiently build one. But sometimes you have to deal with reality as it is, not as you'd like it to be, unfortunately.
Population growth creates the tax base, density, and demand required for a successful public transportation system. Demanding that the public transport comes first is simply backwards.
Listen, I am on the same page as you - I would love for it to happen. I would vote for it. I would pay taxes for it. But the reality is that it isn't going to happen, and if you densify the city without the transit, you will have these problems.
it doesnt have to be subways -- the willamette flood plain isnt great for subways anyway. portland should continue to build out its bus service and cycling infrastructure. portland is already pretty reasonable for living without a car, it will only improve with density.