I don't think anyone here is writing Byron off, they're objectively looking at his performance 3rd year in, and thinking "hey it's time to GET IT GOING". I mean hell, he doesn't even have a Top 5 this year. He's in elite equipment legendary car number, the expectations are high. He showed a lot of potential last year, this season he's regressed, I think him and Chad have started to lose confidence in each other. It's crucial for them to find some form success in this back half of the season, or we could be looking at a CC change for 21'.
Don't care what age you decide to make the jump to Cup, that's your decision, you don't get unlimited time to progress for a decade, that's not how it works. It becomes increasingly difficult to hold onto a struggling driver, realistically if the owner/sponsors are devoted to him, 5-6 years max to find consistent production.
Also for Byron, I think not having Qualifying or Practice is stunting his growth a little bit, and washing out his qualifying advantage over the field. He had 5 poles last year, and seems to be a driver that does well when he qualifies well.
Still have confidence Byron will be able to bounce back, it may be without Chad though. He's run better the last 2 weeks, actually was up front a couple times.