It's visibles that you used to work for an AV company and haven't followed the advances of the industry. As you don't mention any of the modern day technologies like heuristics and file reputation in cloud.
It's true that the world is full of auto morphing malwares, but you can still detect them new variants through heuristics. Which in turn delivers the results to what is generally known as some sort of Antivirus Cloud Lookup or File Reputation Lookup.
Also the AV industry shares information between them. So in the background you don't have anymore analysts looking at every sample file. Instead there's automation that analyses each incoming sample.
The old scan databases you prefer to are usually last line of defense now days if all the other technologies before haven't been able to show the file to be known good file or bad file.
Full disclosure: I currently work for computer security company.