We commonly all seek improved project execution, that is as long as it does not impact the way "I" do things. Let's be honest. We are selfish to a fault, have good size egos and are damn proud of our contribution to the cause, so why would we need to change? But, by the way there is something that you might try to do differently. It is human nature to protect how we individually do things and criticize how others perform their tasks.
If you generally agree with that last statement it should not be difficult to see why the natural operating point of a design team is to maintain the status quo while wishing things would be different. There is no fault or blame to be passed around; its just human nature for teams to settle at keeping things the same. I am not implying that change will not be possible. We must understand and address the natural team dynamics in order to move off of dead center and head in a direction where real change is not only possible, but enthusiastically embraced.
Below is a list of items that must be addressed to enable the teams migration away from the status quo in design team performance and towards a higher level of design execution.
If management does not fully support these items at a minimum, the team will continually fail to meet improvement milestones. As a team leader, manager or stakeholder your mission must be to take charge of the above items, state your case, state your requirements, state your desired results and get them addressed or the teams performance will stay as is.
The harsh reality is that it is your choice to improve or not by first deciding if positive change is a goal or only a wish. If real quantifiable change is the goal then a detailed improvement plan and specific actions must be put in place. Without specific actions in place you are really only wishing for change by default and you can expect a continuing environment of non-productive grumbling about performance and the inability to improve.