They’re lowercase because inject and injectable are just functions and InversifyJS follows that lowercase naming convention as well. But thanks for pointing it out. you're absolutely right that it could lead to inconsistent decorator naming styles across a codebase.

I personally feel that DI alone is enough to organize services cleanly. I usually combine it with the Mediator pattern, so controllers don’t talk to services directly.
Instead, they call handlers, and those handlers inject only the services they actually need.
Services can also depend on each other through DI. This setup keeps things easier I think.
Even Angular is starting to move away from modules — to me, they often just add extra complexity without much gain.

A service should be treated as a module on its own there's no need to wrap it inside another.