The origin of life problem is perhaps the most important question to ever have been the focus of scientific scrutiny. The only other question that I think rates of similar importance is the origin of the universe. Both questions have special obstacles to overcome before any answers are within sight.
The Miller-Urey experiment of the 50s was a lightningrod for research into this question, but the euphoria caused by the viewpoint that the answers were near quickly receded once the scope of the problem was realized and it was decades before the excitement was rekindled in the scientific world. It’s no surprise that the search is a difficult one. Remember, researchers are trying to compress the millions of years that undoubtedly were required for nature to give life a kick start into the lifespan of humans. Couple this with only a limited knowledge of what the conditions were at the time life started except in the grossest terms with the possibility that trace elements may be essential for the synthesis of life greatly compounds the issue. Anyone thinking that if life arose through naturalistic processes means it should be both easy, and that a mere 50 years of research should have resulted in the creation of protolife really doesn’t have a good grasp of the scope of the problem.