I have a 2020 iPad pro 12.9 inch. It's fantastic. It's more than powerful enough for anything I want to do. In fact I was perfectly happy with the 1st generation iPad pro I had before but it died in December and I absolutely could not wait for a new model.Honestly, the only thing that remains is the design and rear cameras/LiDAR. Otherwise, a new device inside and out. Whether or not those with 2018/2020 iPad Pro feel it’s worth it to upgrade depends on their usage.
I can't really think of a reason for anybody with a 2020 iPad pro to upgrade except for a few niche cases. But for vast majority of people dumping the 2020 model for the 2021 one would be 100% vanity purchase.