There is a slight but important differentiation to consider with this question. If the question is, "would the world be better if religion had never existed," then I think the answer would be unequivocally yes. A lot less people would have died, and humanity as a whole would probably be quite a few centuries ahead in terms of progress.
But if the question is along the lines of "would the world be better if religion just suddenly and spontaneously disappeared" then the answer would be no.
In the past, religion has done more harm than good. In the present, it does far more good than harm.
Yes, you could point to Muslim extremism, but we all know the (valid) argument: Muslim extremism isn't motivated by Islam (anyone whose read the Quran knows that). It's motivated by other factors: lack of opportunity, desperation, want to fight for a cause, etc. Those factors would exist with or without religion, so sans religion in today's world, there would still be terrorism.
Yes, you could also point to a sort of Christian extremism here in the states, a set of Bible-motivated views that puts the US far behind other developed nations in terms of social progressiveness. Remember, we have Kim Davis.
But consider that the vast majority of people on the globe are religious. What does it bring them? It brings them hope. It brings them a sense of cause and self worth. It gives them structure and community, and motivates them to do good in the world and have empathy for others. For the average global person, religion is a valuable part of life.
These are things that obviously cannot be quantified, but by any measure far outweigh the harms when you consider the billions that it helps.