In reality, there are three areas of focus, ordered from most potential gains/benefit to least:
1) Midwestern and Rust Belt areas
2) Suburban areas where GOP has no business holding seats (CA, NY, NJ, etc)
3) Sunbelt and/or Southern suburban areas
The path to 218 likely picks seats from all three of these categories, but to not start with the lowest-hanging fruit possible is ridiculous. We basically have a question here that goes like this: "Do we go after the areas where voters have always supported Democrats and still do a large degree down-ballot (but happened to vote GOP for President in the past election), or do we go after the areas where voters have always supported Republicans and still do to a large degree down-ballot (but happened to vote Dem for President in the past election)?".
The answer seems pretty straightforward: we're not in a realignment period just yet.
A point well made. I voted for option 3, but there should be several pickups in California alone without much investing.