Along Bluestreak's points, you could probably make a better case that Davey Johnson was past his prime, Matt Williams was a travesty, and Dusty had some bad breaks and slow reactions in the playoffs than you can criticizing Martinez's handling of 2019. Worst you could say is, with that talent, they never should have been 19-31. Now, I'd take Dusty probably over all of them, especially as a regular season manager, and I think Davey ended up with maybe the worst set of coaches and he exhausted his ability to get the players to improve, but he handled a veteran, high talent team pretty well. This is not a veteran, high talent team, so he had to go, maybe years ago, along with the p-poor coaching staff. That said, this is a LOD thread, so it's ok to focus on how ineffective he was.
As for Mr. Rizzo, if the stat is right that the nats minor leagues the last 3 seasons were in the bottom 3 in xwOBA offensively and K%-BB% pitching, then that's true LOD performance.