Can easycap viewer work on macOS?
The problem you have is that EasyCapViewer 0.6.2 isn't supported on versions of macOS above Mac OS X Yosemite (10.10). In other words, it will work with versions of the Mac OS from OS X Leopard (specifically 10.5.8) up to Yosemite, but won't work on El Capitan or Sierra.

According to the developer:


  2015-10-31: Reports indicate EasyCapViewer doesn't work on OS X El
  Capitan. This would be a good time for other developers to pitch in. I
  will spend some time investigating too but no guarantees.


Source: https://bentrask.com/easycap/

Unfortunately there has not been an update since from the Developer.

In the absence of other macOS alternatives, you may have some joy from using a Windows installation via Bootcamp or via software such as VirtualBox, Parallels, or VMware Fusion.