If you can't interact with a machine that is not listening on port 80 (most home users) how is it possible for hackers to take it over?

I am reading about IP's to improve my AWS knowledge and came across this on reddit:

Now, let's say your IP is 8.8.8.8
. I type it into my browser and press enter. What happens is my browser generates a generic web request for 8.8.8.8
on port 80. Unless you're running a web server like apache and have configured port forewarding, your router won't respond, because it isn't listening for incoming packets on port 80 (or any port). This is good, because it means there is no way for outside users to even talk to your computer or flood it with packets.

Yet still, all around the globe computers of people that don't even know what a router IS get remotely controlled. Did all of them open port 80? Must it be port 80 given that's what the browser will look for, or you can work some tricks to connect any type of port as long as it's open?

Mind you I understand how a computer can become infected with malware that deletes your files. I don't understand how a hacker may "open" a computer for requests from the web.