Not being at the mercy of a company like Oracle is a huge plus in many ways. A huge plus for future development and risk-free adoption.
I use ZFS on a server of mine, but I am one of those paranoid people that would switch just to get away from a project that could be hamstringed at any moment if Oracle has one of its episodes again.
ZFS (hopefully) never finding its way into the mainline kernel is kind of a meta-disadvantage.
They can't just relicense OpenZFS. The only attack vector is suing Ubuntu for distributing zfs because Canonical's lawyers think that's fine but even then, you're still free to use it by adding it to the system yourself like any other distribution is doing.
Running a new filesystem is far more dangerous than your theoretical legal concerns.
The thread you linked is someone who was using software with a proprietary license against its terms and is being asked to pay for its usage -- obviously I think Oracle is being scummy but it's not a comparable situation at all. This would be like saying that you won't use VS Code because Microsoft once demanded that someone who was using a cracked copy of Windows pay them -- it's a complete non-sequitur.
Would you refuse to use ZFS on FreeBSD as well?