> Voting right should be earned.

The problem you run into is that someone has to define how it should be earned. Several criteria have been tried (wealth, tax paid, military service, etc), and all of them have been found inadequate in one or several respects.

Several revolutions have been fought over this. Still, assuming that a perfect criterion would exist, what would be yours?

Mine would be qualified service to society. 2 years of public service, with no option to bypass. Service being tailored for your particular skills and abilities.

This is already much more sensible than paying above a threshold in taxes, or owning a certain surface area of land, or coming from the right families. We'd have to define "public service" in such a way that absolutely everyone could perform it, including for example disabled people. Otherwise, it's just a requirement to have been fit (and male, in most cases) at some point in your life.

I am unaware of any definition of the phrase "public service" which requires physical fitness or masculinity. We are not talking about military service here.

The dictionary definition I pulled up quickly is:

   1. Employment within a governmental system
   2. A service performed for the benefit of the public

I cannot imagine how #2 could be any more inclusive than it already is. If anything, the current definition is overbroad, to where almost anything could be spun as public service.