Compared to React + React DOM at 109k unzipped Blazor's runtime at 2MB is a significant hike in download size so unsuitable for older devices and constrained bandwidth networks.
2. 2MB includes bootstrap CSS and they are working on getting that number down.
3. 2MB is only the Wasm version of Blazor. You don’t have to use that version if it doesn’t fit your use case.
Most people I've talked to using Blazor are in fact using Blazor server not Blazor WASM.