Stencil aims to combine the best concepts of the most popular frontend frameworks into a compile-time tool rather than run-time tool. It's important to stress that Stencil's goal is to not become or be seen as a "framework", but rather our goal is to provide a great developer experience and tooling expected from a framework, while using web-standards within the browser at run-time. In many cases, Stencil can be used as a drop in replacement for traditional frontend frameworks given the capabilities now available in the browser, though using it as such is certainly not required.
There are countless optimizations and tweaks developers must do to improve performance of components and websites. With a compiler, Stencil is able to analyze component code as an input, and generate optimized components as an output.
As the world of software development continues to evolve, so too can the compiler. Instead of requiring complete rewrites of components, the compiler can continue to make optimizations using the standard component model as the common input. The compiler allows developers to create future-friendly components, while still staying up-to-date on the latest optimizations without starting over again and again. Additionally, if something changes about any API, the compiler is able to make automatic adjustments and notify the developer exactly what needs to be updated.
Stencil purposely does not come with a large custom API which needs to be learned and re-learned, but rather heavily relies on, you guessed it, web-standards. Again, our goal is to not create yet-another-framework, but rather provide tooling for developers to generate future-friendly components using APIs already baked within the browser. The smaller the API, the easier to learn, and the less that can be broken.
If you haven't noticed already we think web-standards are great and offer many benefits. While using web-standards without any structure is certainly possible, and there are actually many use-cases where this would be appropriate, we found that as apps and teams scale it quickly becomes difficult to manage. Developers often gravitate to frameworks because of their great tooling, defined structure, and ability to allow developers to build apps quickly. One of the largest goals of Stencil is to be that intersection of having great framework features and first-class tooling during development but generating future-proof web-standard code, rather than custom framework specific code.