https://en.m.wikipedia.org/wiki/Golden_rice
The controversy section is very telling. While not directly quoted in the article, I've seen/heard people argue, "It hasn't been proven safe!" Well, yeah? Of course it hasn't. Nothing is ever proven safe, really. It'd be much easier to demonstrate the benefits if, you know, they actually let trials go forward.
Some trials have been started, but people keep protesting and doing stuff like burning the fields.
That's not the reason why Golden Rice has been a failure[1]:
> While activists did destroy one Golden Rice test plot in a 2013 protest, it is unlikely that this action had any significant impact on the approval of Golden Rice.
> “Destroying test plots is a dubious way to express opposition, but this was only one small plot out of many plots in multiple locations over many years,” he said.
Rather:
> As Stone and Glover note in the article, researchers continue to have problems developing beta carotene-enriched strains that yield as well as non-GMO strains already being grown by farmers.
[1] https://source.wustl.edu/2016/06/genetically-modified-golden...