There is a place for copyright.. just not anywhere near as broad as it is now.
I'm a firm believer that if you use a work in a commercial way (or a derivative work in commercial way for financial gain), for financial gain, then yes, the original artist should be paid and should decide how their original work is used. This is because someone is making money on someone else's hard work, and that's not on
However if your not, then there is no foul and shouldn't be fined/imposed a fee upon, and be allowed to share (again as long as there is no financial gain)
Einstein put a lot of work in to the theory of relativity. Also, I think it was him who did much of the theoretical groundwork for the development of the laser, but without figuring out the final step of how to manufacture one. Two others figured out the final step at much the same time, and fought over the patent rights, while paying nothing for all the previous work. In some sense, I think everyone does deserve to be paid for any work they do that someone else benefits from, even if they didn't have a contract for it, but I'd stop short of saying they have a right to extract payment by force. If you don't stop short of this, then how do you decide what kinds of work entitle people to extract payment by force from those who benefit?
As for GPL, I believe it is just as restrictive as what it is trying to replace. And if you don't follow GPL to the letter you can get buggered over (See VLC app getting pulled from Apple App Store, therefore millions cant use this excellent piece of free software, for no reason alone other than the GPL was incompatible with Apple (and infact it wasnt Apple's choice to pull it, it was ONE PERSON from the original team of creators)
AFAIK, Apple would be permitted to distribute VLC without paying for it if they wanted to, if they didn't DRM encode it, whereas they wouldn't be permitted to distribute MS Office without paying for it, regardless of whether they DRM encoded it or not, so I'm hard pressed to see how the GPL is just as restrictive.
there is no need for a "copyright monopoly", as it should be a simple agreement between the original creator and the one using it to make a financial gain (whether large scale or not)
Whether the copyright holder has an exclusive right to issue copies, or an exclusive right to issue licenses, I think it would still be a monopoly.
The app was free, now no one can use it
explain to me the benefits for the end users again?
AFAIK, the intention is that by disallowing people to take GPL works and encode them with DRM, or offer them without source code, it is disallowing people from using GPL works as a means to gain power/control over others. But in any case, you never said copyright was supposed to be about benefits for end users, you said it was about payment, and in the case of the GPL, the authors want to be paid in terms of source code and DRM-free access.