I get it, it just doesn't seem logical to me for a few reasons. Just to get the Arch Manning concept out of the conversation, he's a redshirt freshman. His family, especially Eli, have been pounding it into his head to stay in college and not entire the draft until after his senior year, which so far, he's been listening to their advice (look back him considering entering the transfer portal and Eli telling him no, to stay as Ewers backup). So it could be till 2028 when Arch enters the draft. None of us have a crystal ball so its hard to say.
To the rest of the post, the players have checked out, its true. We all see it. But the cap is in shambles. We have no draft capital. Its hard to imagine what good potential coach would want to come here next season even if we wait till the offseason to fire Dennis Allen. We'd likely end up with another below average or bottom of the barrell coach.
To top that off I think you're greatly misunderstanding what "the message" your sending impact really has. The players have "silently quit" already. Firing a head coach mid season is also incredibly dramatic. I think its unreasonable to expect people who have silently quit, to be introduced to a turmoil of drama and expect them to re-engage with any enthusiasm. Yes, it seemed to occur with the Raiders last year when Pierce took over, but its also having a negative impact on the Jets this year. And from what we've seen in the past, it rarely, if ever, has a positive outcome.
And again, you're adding an additional factor for the next head coach to consider when accepting the job. Why would Ben Johnson, or Aaron Glen accept this job when there are more stable front offices, with less drama and better cap situations pining for em? Anyone who comes in after DA will be set up for failure.