Was it ok to add an outlet on a home run in the attic?
What you did is just fine. That is what any experienced electrician would have done.

If all of the wire in the entire circuit is #12 you could change your breaker to a 20 amp breaker for more capacity. If any of it is #14 you have to stick with the 15 amp breaker.

The previous setup is a waste of wire. They could have put one junction box in the middle of the room and dropped to each box OR they could have hit one box and then daisy chain to the other three boxes through the studs if the room only had one door.

There are many ways to get the job done and sometimes it is just a personal preference.

Your setup is fine though.
Good luck!