There are generational performance leaps, and then there is pure marketing. The Core i9 series has so far been leaning towards the latter in terms of raw performance. In some cases, the CPU may even be slower than the Core i7.
https://www.notebookcheck.net/Some-Intel-Core-i9-laptops-are-not-running-any-faster-than-a-Core-i7.317268.0.html