something that people forget with raid1 is that this only protect from catastrophic disk failure.

this means your your drive need to be dead for raid to do it's protection and this is usually the case.

the problem is when starts corrupting data it reads of writes. in that case raid have no way to know that and can even corrupt data on the healthy drive. (data is read corrupted and then written to both drives)

the issue is that there are 2 copies of the data and raid have no way of telling with one is correct so it's basically flips a coin and select one of them, even if filesystem knows that content makes no sense.

that's basically biggest advantage of filesystems like zfs or btrfs that manage raid themselves, they have checksums and that know with copy is valid and are able to recover and say that one drive appears healthy but it's corrupting data so you probably want to replace it