You don’t define bitrot. If you leave software alone with no updates for long enough, yes, there will be problems.
There will eventually be a security issue with no fix, or a new OS or hardware it doesn’t work on.
Backups can also fail over time if restores are not tested periodically.
This recently happened to me. A server wouldn’t boot anymore, so we restored from backup, but it still wouldn’t boot. The issue was that we’d introduced change that caused a boot failure. To fix that by restoring from a backup, we’d need a backup from before that change. It turns out we had one, but didn’t realize what the issue was.
The other moral is to reboot frequently if only to confirm the system can still boot.