He has five 20+ goal seasons. Moore has 1. He has seven 40+ point seasons. Moore has 2.
And Moore has been seriously struggling this year while Rakell has been having a great year.
Saying Rakell is barely an upgrade over Moore is a pretty questionable take (respectfully).
Rakell is a clear cut top 6 forward - Moore is a solid 3rd liner (or middle 6 forward when he's on). Also, Rakell is a right shot who can help the Kings powerplay - just on handedness alone Rakell would be a solid upgrade over Moore.
I do question whether it's worth giving up the 1st or not and I'd love if the Kings could find a way to get the deal done without a first - But with the year Rakell is having, the fact that he comes with a very reasonable $5m cap hit for this season + the next 3 seasons, and the fact that he's one of very few right shot scoring wingers potentially available on the trade market - You might have to bite the bullet and send the 1st to get the deal done.
I was also trying to make this deal as fair/realistic as possible. If the mock trade included something like a 2nd and a 4th instead of a 1st - I'm sure people would be telling me to pound sand lol.