Depends on the organisation as I've seen the opposite (excessive planning without taking action) too. I'm on the speed side of things nowadays because I was usually wrong when I thought that the "work is understood and the constraints are clear".
Yes, the problem is the feedback loops often don't really exist in the planning stages. It is more difficult to gauge progress. There can be very detailed specifications or plans that won't survive their first contact with reality. This is why waterfall is over with.
Yet - not planning effectively is also a huge problem.
