You say trivial comparisons but that is a pretty reductionist view of what a database can do. I assure you there are more than trivial comparisons going on. Distributed joins, aggregations, and even sorting is not a trivial comparison.
So how can the GPU help?
1. Data in datalakes is often compressed. These compression schemes are often amenable to being decompressed directly on the GPU. It is faster for most columnar compression schemes we see in files like Parquet and ORC to be decompressed on the GPU rather than on the CPU.
2. There are many distributed caching strategies which would let you make fewer and fewer requests directly to your data lake. If you are really clever, you might even decide to store a more compressed representation in your cache than the actual files you are reading from. This was not so difficult to do for data formats that already come in chunks like Parquet and ORC.
What workloads is it good for?
Ones where the consumer will be a distributed solution that runs on GPUs, a non distributed GPU solution coordinated by a tool like DASK, or even a single node solution where the user is going to be using other tools from the rapidsAI ecosystem. You use this if you are already leveraging the GPU for your workloads and want to reduce the timeline of getting data from where it lies, to the GPU.