I shall make the case for each:
Sherrod brown: Serious candidate, made motions towards running, is polling in top 5 already without even having lifted a finger.
Ojeda: Already announced hes running, and could potentially make waves on the debate floor. If you've got the ROCK on there, you should include someone whos Actually running
Julian Castro: Basically running, hes announced an exploratory committee, and is likely to run on January 12th
Jay Inslee: Similar boat to Castro, hes definitely thinking about running.
Jeff Merkley: hes keeping his cards close to his chest, but he seems to be making moves towards a 2020 run.
Richard Ojeda is literally the only person that has actually declared he's running for President. Some of the others have launched "exploratory committees", but he was explicit.
There's no excuse to not have him on there.