I agree with this. The Death of Superman arch shouldn't have taken place with Justice League as his next appearance. Preferably it would have been in a solo movie, after Justice League 1. Makes more sense for many, many reasons. The major reason being that they would have had more time to flesh out the character, build up his status as a hero and get the audience behind his character so that it would have more effect on the audience when he died.
BvS made alot of mistakes but I think it would have been alittle better received had it come further down the line in the world building, where it makes more sense to the audience, to see Batman's career, his frustration building with so many of his allies turning against him, criminals continuing to show up despite his best efforts, some failures and tragedies along the way to make him lose his way and for Superman to build up his status as a symbol of hope and inspiration so that his death felt more like a loss, rather than a timeout. It all felt incredibly rushed and contrived.