Poor Daniel Gafford is really getting screwed by Jordan Poole.
I noted that Poole's horrific net rating isn't really all that bad when he shares the court with Gafford. With Gafford alongside him, the net rating is merely -12.2, way better than the -18.6 rating for all of Poole's minutes. It turns out, Gafford has been doing a yeoman's job of keeping the team afloat.
As soon as Gafford sits, the team just totally falls apart. In the minutes when Gafford sits and Poole is still on the floor, the net rating declines all the way to -30.7!
Poole's defense, unmitigated by Gafford's rim protection, is an apocalyptic disaster!
Meanwhile, in the 96 minutes when Gafford is on the floor and Poole is off, the Wizards have a respectable net rating of just -3.9. This is noteworthy because these minutes are presumably mostly against starting-caliber competition. It's a small sample size, but our non-Poole starters, when facing the opposition's starters, are actually respectably competitive.
(It's one thing to note how well the team plays without Poole, but that's mostly just saying our bench is competitive with other team's benches, which is nice, but nothing to write home about. The Gafford numbers suggest that our starters are competitive with other starters, as long as Poole isn't dragging them down. And that's a much bigger deal.)
The TL;DR version is: bench Poole and never play him again!