In this specific scenario it's two things:
1) 3rd gen brings large (20+ perc.) IPC increase, and also clock-speed increase. So you get much faster single-core performance, and everything is still mainly single-thread operated, including 3dsMax. Even during IR, you will be doing single-thread operations while the PC is rendering. The overall experience will be much smoother.
2) 2970WX and 2990WX had very specific, compromise-born architecture with multiple NUMA (memory access), and also only two our of four dies had direct access to memory controller, the other dies had to first go through their "siblings". Depending on workload, there was serious performance penalty. And also it took quite long until Windows Scheduler learned to use the correct cores and I doubt it works well even now.
Looking back, 2990WX as chip was largely a mistake. The rendering performance was fantastic, and the price-value was something phenomenal, but it had way too many issues because of its design. 3rd-gen Threadrippers, feature absolutely zero such compromises, all dies have direct access to memory controller with centralized IO, and they use UMA (effectively single NUMA node).
With that said, people who experience crashes with 2990WX probably have wrong motherboard, wrong memory or sometimes both. 2990WX had only two good boards, and it was very selective in memory speed/timings.
Again, no such issues with 3rd-gen, all the boards are great, and you can run almost any memory.