I actually consider anti viruses to be worse than just following basic security protocols. They slow down your computer, they often come with bloatware, and they're intrusive via unnecessary notifications. Also, some people have claimed they falsely identify problems, just so you think they're working.
As someone who has tried at least 15 or more commercial home AVs over the years, I can say that there are indeed those that are difficult to configure, have an impact on the system, and can cause inconvenience to the user. However, there are security solutions that are the opposite, and their presence on modern computers is almost invisible if we look at CPU or RAM usage.
For example, I will say something about my experience with Norton Security, which I consider almost perfect. RAM consumption is generally less than 100 MB, while CPU goes from mostly 2-5%. By comparison, Firefox with 4 open tabs consumes over 1 GB of RAM and close to 10% CPU. For a computer with 8 GB of RAM and a modern processor, no AV will be a problem with resource consumption.
I agree that protection depends on what the antivirus definition database is and how often it is updated - but also on how good
heuristic analysis it has, which means that it can fight against those threats that have not yet been added to the antivirus database.