I think you might be taking it a little too literally
1. https://research.lifeway.com/2020/09/08/americans-hold-compl...
If you were unaware, belief that Christ died for our sins and was resurrected is taught as the prerequisite to salvation and entering Heaven upon death. Given this fact, I would expect 100% of Christians to believe this.
As an additional note, modern Christianity (except maybe Catholicism) brush a lot of the old testament under the rug, of which includes Ecclesiastes I believe? Some churches teach Matthew 5:17 as support for doing so. Catholicism seems to have a more nuanced take: https://www.catholic.com/magazine/online-edition/did-jesus-r...
Who cares?