Imagine not having a waste management system: you'll end up with garbage everywhere. Hence, you need to invest time to do garbage collection (and perhaps permanently solve the problem by introducing garbage bins, garbage trucks, etc.). You can take the metaphor further :)
Oh just to add, each OS probably has several implementations of Keepass, you'll have to search for one for your respective platform. KeePassXC just happens to be the one I use on Linux and then I've got KeePassDX for my Android devices.
Anyone that needs to be maintained for a long period of time. For example: Firefox.
Today Firefox have all the rust deps bundled (similar to cargo bundle). If / when tomorrow the maintainer of the distribution find a bug in one of the rust dependencies, s/he needs to add the fix inside the bundle without a clear process (1. do I need to fork and update Cargo.toml to point to my branch? 2. can I add the fix as a .patch and apply it after it gets unbundled by the build server? 3. ...)
An also this process needs to be repeated for each application that have this version of the crate as a dependency, and again without a clear way of identifying those applications that are affected.
Its more light weight and usually doesn't enforce any particular way of doing things. Regardless of warp support, I have most of the other things on your list integrated one by one (JWT/dashboards /react/diesel) but it was time consuming as I didn't have a quick start project template.
So I think the work you are doing is going to be valuable for the community. I guess giving an option between the three popular web frameworks (actix, warp, rocket) won't be so easy as you might have very different way of integrating the authentication etc with each. Probably one way to do this is to keep things more modular so that the authentication can be called independently (among other features).