The 'write' part would technically be very doable and not that different from other back-ends.
My more recent prototype shrinks that to 10.47 MB transferred: https://simonw.github.io/research/pyodide-asgi-browser/datas...
You almost never need just a basic list of all the data in your table, even if you're able to filter and sort it. There's no moat there at all. People need serious BI tools, and that throws simplicity out of the window (PowerBI, QuickSight, etc.).
In reality, what most people need is much simpler, a mini app with some curated datasets and simple filters, maybe some AI querying if we want to get fancy. There's some companies out there that work with big data, but for the rest of us small data is ok.
My phone has 1TB of storage.