For reference, I just looked up the benchmarks for the i7 3840qm. Seems to perform in the same ballpark as an i5 10210u for multicore, which is the base cpu in the current thinkpads. Intel really hasn’t made faster cpu’s in a long time.
The 3840QM has three times the TDP of a 10210U. A modern 45W part is going to be that much faster. Meanwhile the modern 15W part is also going to be a lot better in bursty single core desktop workloads.