why Se types seem to make things look easy
...to Ni types, at least.
Se types are static. They either see a task or project as done or not done. If it's not done and needs to be done, they get it done. It's that simple.
Ni types are dynamic. They envision a project as a series of things they will need to do instead of simply "done" or "not done". Completing the project seems more complex or energy consuming to the Ni type, even if they are every bit as capable of completing the project as the Se type.
(Obviously, Se types are capable of seeing the steps involved in the completion of a project, just as Ni types are capable of understanding that a project is done or not done. The idea is that they're likely to view the project from one perspective more so than the other.)