It was a different world, home computer security wise, back in the early 2000's. People were still often being hooked up to the internet with those old Motorola Surfboard modems (the single ethernet jack ones) and having that directly connected to their computer. That allowed direct attacks to be done against their computer. In addition, MS shipped Windows XP back then with services running by default that were NOT secure (such as uPnP). That led to the depressing situation of people, right after OS install, downloading security patches to fix those holes while at the same time the computer was being attacked (and exploited) with those holes
The modern situation is massively better. Nearly everyone anymore is using a router (or router+modem combination). The router normally has a simple firewall that protects everything on the network in your house. Also, both Windows & MacOS now have more risky services disabled by default and have a personal firewall active by default on your computer. In addition, both OS's have patched their other holes. While no security is 100%, there's a good reason you heard those stories 15+ years ago but you haven't heard much about those kinds of attacks any time recently
Note: If you want to improve this portion of security, then you'll need to read up about firewalls. Keep in mind that most people don't really need ANY ports open into their network, just the ports open to go outside of their network. (IOW, your computer can reach out for things, but outside computers can't reach in)
One other thing: In the last 5 years or so, MacOS showed up with a couple of security holes that Apple rated at a high severity level. They not only patched them for supported OS releases, but also for the last major unsupported. In this case, that would still be High Sierra. The reason Apple did this, is because a lot of corporate customers were still running the unsupported OS. No idea if they'll do it again, but it's likely
Keep in mind this: in recent security conferences, EVERY OS has been hacked. Every last one of them. That includes the latest Windows 10, MacOS Catalina, iOS, Android, and every major version of Linux. MacOS High Sierra is basically as secure as any of them. What you need to depend on is hardening what I mentioned before: email, browser, any other applications installed, and maybe the firewall in the router. Do that, and attackers won't be able to reach your computer in the first place
