Improving a league bottom secondary, in this NFL, helps the offense.
For a young QB learning a new offense, quick routes/checkdowns are a best friend. Especially when as you say, the line remains bad [they literally added a starter and depth tho]. Velus Jones IS THOSE ROUTES PERSONIFIED. His whole game is get the ball quick, make things happen. He can walk in and do that, and the staff plans on using him as such.
Would I have loved a WR early? Sure, but not going to get a WR1 or 2 at that spot, and they likely instead got two day one starters for a terrible secondary.
So yeah, I stand by my comment on your naivete.