That's been true as long as treatments for cancer have ever been researched (reaching back to the 1800s). Only recently have immunotherapies started yielding si

That's been true as long as treatments for cancer have ever been researched (reaching back to the 1800s). Only recently have immunotherapies started yielding significant clinical results for common cancer types. I think the change in efficacy has a lot more to do with the accumulation of scientific knowledge about the immune system (it hasn't been long since we even discovered T-cells or dendritic cells), along with huge improvements in genetic sequence & editing.