The cloud apps are not slow only because of moving data, but there is also a problem that an average server is fast(16cores CPU + 64GB RAM), but If it's used by let's say 100users, It means one user has only 0.16core + 0.64GB memory. So an average laptop(4cores/4GB) or phone(4cores/1GB) is way faster. Basically people buy billions of transistors to use them only as a terminal to the cloud. Not to mention privacy risks.
A week ago, I did showHN for skyalt.com. It's a local accessible database(+ analytics, which is coming soon). I'm still blown away how fast it is, that you can put tens of millions of rows to single table with many columns on consumer hardware and you don't pay for scale or attachments.