Totally different API, Sqlite is SQL based while IndexedDb is a key/value store with indexing and transaction capabilities (essentially the bare minimum on which a relational database could be built, the irony).
If your model is highly relational then it doesn't matter that querying for one entity is fast when what you really need is to, for example, efficiently join together multiple entities, grouping on N columns to produce some aggregate result. This is completely straightforward in SQL, but a convoluted inefficient, error prone mess in the alternative.
> IndexedDb is a key/value store with indexing and transaction capabilities (essentially the bare minimum on which a relational database could be built, the irony).
It's not ironic at all, it's just a good application of the extensible web manifesto : the browser support minimum necessary building blocs and then libraires can enhance the developer experience.
