It's important to note that you can still run unsigned Mac apps. Apple isn't preventing users from running a tool they want to run, it's just showing them a big scary warning and making them jump through some extra hoops.

It's incredibly scummy and inappropriate, but I would put it more along the lines of an attack-ad than an outright ban.

Edit: Now, one thing that isn't totally clear is whether or not devs who have their own developer accounts, and use Unreal Engine to target iOS, can still make iOS builds. If not that's a much bigger deal, though the fundamental issue would still lie with iOS, not macOS.