If you have unskilled people who work poorly together, no amount of process will save your projects.
A methodology's weight is a product of its size and ceremony.
Process is not a substitute for skill.
If you find that your organization can't make the hard decisions that Scrum demands, then high-risk, uncertain projects have very little probability of success in your organization.
The best way to get a project done faster is to start sooner
Peel back the facade of rigorous methodology projects and ask why the project was successful, and the answer is people.