1. Reddit's internecine subreddit wars required constant admin intervention and mediation. Reddit only has so many hands on deck, so more of than not, they pulled engineers in to help moderate.[1]
2. Reddit is unprofitable, so they have trouble affording top talent. [2]
3. Finally, Reddit's vision for the future has been hazy for the last decade. If the navigators can't chart a course, all the rowing in the world won't move the ship in the right direction. I suspect the overdone April Fools experiments are a result of engineering not being given technically compelling, or perhaps meaningful features to labor over.
Sources:
[1] https://www.reddit.com/r/TheoryOfReddit/comments/58zaho/the_...
[2]http://www.thedrum.com/news/2017/04/02/reddit-sets-eyes-prof...