Minecraft won't launch, pop up error says can't update native launcher?

We're trying to launch Minecraft from a macOS 10.11.6 (el capitan) on an iMac. When we do this, it tries to load but pops up with a message saying it can't update native launcher. We have played Minecraft perfectly fine up until this point, within the past 48 hours without any issues. There were no obvious Mac updates and my launcher on my PC laptop is working perfectly fine still. We have tried uninstalling and reinstalling Minecraft several times. Rebooted the computer. No AV active and firewall is disabled. We uninstalled and reinstalled java as well. We're at a loss, please help?

Yeah, I wouldn't play Minecraft on an iMac. If you have the money to buy an iMac, you should be able to build your own gaming computer.

"There were no obvious Mac updates"

That's because you're running an outdated version that hasn't been supported in over a year. Try upgrading to a supported version. It's unlikely the developers test it on unsupported operating systems, so it can break on any update.

If you use a loader, it may have interfered with the update.
delete the installation, and load from scratch.