Based off of the table below (strictly for Jordan Poole) can I draw the conclusion that because his OnCourt +/- is way better than his On-Off +/- that he isn't the first person to blame as to why the Wizards are so bad? If that is incorrect, what conclusions can I draw?
No - the On-Off is showing that the team has been 37.2 per 100 worse with him on the court than with him off the court. Using his OnCourt number there, you can figure out that the Wizards have been +14.1 per 100 when Poole is not on the court.
Other than some rounding being used differently between the two pages (as this is showing a +14.0 with him off and -37.1 on-off for him), you can verify that here: https://www.basketball-reference.com/players/p/poolejo01/on-off/2024