I don't know how to quantify "national appeal", but the Post had about 2.5 million paid subscribers in 2023 and ~800 newsroom staff, while The Atlantic had about 1.1 million paid subscribers and ~200 newsroom staff.
Now the Post is down to ~2 million paid subscribers and 500 newsroom staff.
I don't think the Post was known as a slanted project for "the political opposition" during red or blue administrations, but it's got that reputation now.
My claim is that this new slant is responsible for the bulk of the paper's loss of paid subscribers. There's a market for rigorous, fact-checked reporting. Degrading that makes the business worse, not better.
What's the other national American newspaper --- not newsmagazine, 95% of what the Atlantic runs isn't reported --- besides the WSJ that's doing well right now?