Excel is not really capable of utilizing more than one CPU core, and doesn't use the GPU at all for spreadsheet recalculations, so it's not too surprising you didn't see much change. Unlike Intel Macs, all M1 Macs have nearly identical single-threaded speed. ("Nearly" because plain M1's highest single-thread frequency is 3204 MHz, and M1 Pro/Max bumped that to 3228 MHz, which is only a 24 MHz gain.) The only thing the Max has which can help is more memory, but if your dataset fit in the base M1's memory just fine, that's not an advantage either.The M1 Max is somewhat faster than the base M1, but I still get regular beach balls in our Excel Model. The increase in speed is not night and day either. What’s odd is that the CPU isn’t typically maxed out, except briefly when filtering and unfiltering the large datasets. But I don’t see the CPU really struggling, especially when it beach balls. It is annoying that the M1 Max doesn’t solve the issue.
As a rule of thumb, if you are using Excel to do heavy computation on large datasets, you are probably using the wrong tool for the job.