It was just 3 years ago, in the 2020 season, that the 49ers finished 6-10. So it could happen. And I know Jimmy and Nick Bosa were injured. But the point is that there is always a path to a losing season in this league. It's hard to win games in the NFL.
Here's a path for the 49ers to end up 5-12:
1. The offensive line, with Trent Williams and basically no one else, takes a huge step back, as predicted by PFF:
https://www.pff.com/news/nfl-offensive-line-rankings-2023-offseason.
2. The defense falters under Steve Wilkes, who is not DeMeco Ryans or Robert Saleh. His Carolina defense last year was 19th. He did coach a good defense in Carolina under Ron Rivera in 2017, but that was largely Sean McDermott's defense that he took over when McDermott left to coach the Bills.
3. If having 2 quarterbacks is like having no quarterbacks, then what is having three QBs? If the QB situation ends up being a shit show, it's going to divide the locker room and cause all kinds of issues.
4. CMC isn't as productive in year 2 because it's his seventh season as a running back in the NFL and at some point, you just lose your hops and you're not as effective. Deebo Samuel is the same player he was last year, and isn't the superstar receiver they pay him to be.
5. Javon Hargrave, it turns out, wasn't the best lineman on the Eagles after all (although we already know this). Having been paid, he's no longer hungry and turns in a desultory season.
I'm not saying any of these things will happen or is likely to happen, just that this is one way in which the 49ers could easily finish 5-12.