Trinity and non trinity systems don't need to replace each other, or cancel each other out. Claiming otherwise is foolish and blind fanboyism to either system.
The trinity has many advantages, which I won't bother to analyze here, as they're easily found on the web, so saying that it dumbs games down or that it serves no purpose proves you have absolutely no clue about how MMORPGs work.
Regardless, GW2's approach of non-trinity is lame and a gimmick.