It's actually not.
I effectively did just what you described. My 2019 i9 iMac has 128 GB RAM with just 8 CPU cores. And I need that 128 GB RAM purely for single-core operations (calculations in Mathematica).
Needing lots of RAM for single-core operations is not uncommon in scientific work.
Hell, even a 4-core 14000-series i3 can support 192 GB RAM:
Intel® Core™ i3 processor 14100 (12M Cache, up to 4.70 GHz) quick reference with specifications, features, and technologies.
www.intel.com
So if you're someone who needs lots of RAM but not lots of cores, if you want to work in MacOS you need to significantly overbuy on the CPU.
Fortunately, things are improving. With the M1, you had to buy an Ultra if you needed 128 GB RAM. Now you can get that with the Max.