"data security and rot resilience only goes for systems with ECC memory."
No. Bad HDDs/SSDs or bad SATA cables/ports cause a lot more data corruption than bad RAM. And ZFS will correct these cases even without ECC memory. It's a myth that the data healing properties of ZFS are useless without ECC memory.
I once managed to use ZFS to detect a bit flip on a machine that did not have ECC RAM. All python programs started crashing in libpython.so on my old desktop one day. I thought it was a bug in ZFS, so I started debugging. I compared the in-memory buffer from ARC with the on-disk buffer for libpython.so and found a bit flip. At the time, accessing a snapshot through .zfs would duplicate the buffer in ARC, which made it really easy to compare the in-memory buffer against the on-disk buffer. I was in shock as I did not expect to ever see one in person. Since then, I always insist on my computers having ECC.
Precisely this. And don’t forget about bugs in virtualization layers/drivers — ZFS can very often save your data in those cases, too.