This is an area we want to improve in the future. Most of the JS libraries can be disabled in the project configuration. We find that our typical user prefers to have access to the features those libraries provide, but I agree with you that we should be doing better. This is a place where some guided documentation would help. We're working on it.
With that said, we dogfood Quarto pretty seriously, and consume the content from mobile devices. I admit that we use devices that are likely in the 90% percentile of speed, but website performance is something we do take into account.
We do generally attempt to only include JS dependencies in the HTML output if they are used. We share those dependencies across pages in a website, so if a single page uses a dependency they all will pick it up, but if you have a minimal world view and disable the various interactive goodies, you should get a _relatively_ more thin set of dependencies.
For HTML output, using `minimal: true` in document front matter will give you very minimal HTML that should be ready to style with CSS (and pretty much no dependencies)
The complication is from the implied dependencies. If you've designed from zero to be able to track the requirements everywhere in the code base, then that's (in principle, though still not trivial) possible. But if you're looking to ship fast with a small team on the large feature set that we do have, then it's actually a better call to work on a system that has a fixed set of dependencies known in advance, and quickly iterate to solve other customer problems.
tl;dr: tradeoffs. We chose one that still serves us well, but it does come with consequences.
This is an area we want to improve in the future. Most of the JS libraries can be disabled in the project configuration. We find that our typical user prefers to have access to the features those libraries provide, but I agree with you that we should be doing better. This is a place where some guided documentation would help. We're working on it.
With that said, we dogfood Quarto pretty seriously, and consume the content from mobile devices. I admit that we use devices that are likely in the 90% percentile of speed, but website performance is something we do take into account.