Seeking consensus can support change by increasing buy-in, communication, and active listening.
But, consensus doesn’t mean 100% agreement of all those impacted by a decision.
In practice, it often means that major stakeholders state their opinions, trade-offs are made, and a path is selected. That path may be agreed upon by many of the participants, but not necessarily all of them.
When considered a substitute for decision-making (as opposed to a supplement), consensus can impede progress and reduce flexibility.
To make matters worse, consensus can be confused with communication. People are included in the pursuit of consensus only to insure they’re “in the loop.”
In my experience, when trust, respect, and open communication exist within an organization, decisions can be made outside of committee.
I’ve actually worked with more for profit organizations than nonprofits, but your last point really hits home in any case “it takes four times as long and costs twice as much.”
This is particularly a problem in nonprofits. They confuse consensus with 100% agreement – and everyone has to “feel good” about it all! (Group hugs optional.) So, nothing ever actually gets done – or if it does, it takes four times as long and costs twice as much.