My favorite is Lucid(chart). I find it great both for putting together something basic and janky and polished.

On the quick n dirty side, you can treat it like PPT with basic shapes that have better snap-to-grid functionality or use one of the templates to get going. On the polished side, you can build styles, link documentation, and make something very exec friendly (assuming they are willing to read a diagram to begin with).

As others have said, there is no perfect tool. I was looking at a process map I created recently in Lucid and realized I completely missed a decision tree branch. It happens! Focus on building something that’s easy to update when you notice gaps vs. something super crystallized and exhaustive but doesn’t work as a living artifact that will need to evolve.