No. It's not so easy because in most cases you have to choose between security, flexibility and usability. Obviously it's not a 100% accurate example but generally speaking, it tends to be true. Sum it up over several decades of development and you get why we cannot have something that it's really really easy to use, flexible and secure by default.
Which would help exactly 0 in this scenario, where someone is exposing a port directly on the Internet. Also, FreeBSD is even more niche than Linux, I doubt it would stand the average user stress test.
Absolutely it would because jails doesn't do weird shit like this from the get go.
With FreeBSD, you have to deliberately open ports, not the other away around.
I don't understand your second sentence.
"average user stress test"??
> With FreeBSD, you have to deliberately open ports
The issue outlined in the article happened because the author deliberately open their service to the public internet. Replacing Linux with FreeBSD wouldn't have prevented the compromise.