I think most of the criticisms of previous coaches just come from ignoring contexts and circumstances.
Be that as it may, most good coaches do not start out well. Look at Shanahan this year. The same good coach all year. Then the wins came when he got a qb.
So to me what 2017 proves is that even good coaches need talent.
McVay inherited a ton of talent. That includes a young ascending franchise qb and TWO players who were in the conversation for league MVP. And that's just the tip of the iceberg.
You can probably mark this down as a law of physics
but...if you see a one year turnaround, it is because the new coach inherited a lot of talent.
I really can't think of any exceptions to that.
...