Much of that can be owed to the fact that Red is just a tough color to make work in Commander since its effects don't tend to scale very well to four-player games, but Prosper gives a very clear direction
They don't often run a lot of artifacts that are going to sit around and not be tapped, and Soldiers in Standard is almost exclusively Mono-White, and only sometimes splashes Blue, so I don't think he's going to find his way in there
Primal Genesis (Naya) The upgrade path here is to go full Giant Adephage: Spawnwrithe, Spitting Slime, Polyraptor, and friends
Adding a bit of randomness and a small tax to your combo piece, board wipe, draw spell, or whatever else is definitely not that big of a downside
The main reason is that most players recognize cards through the artwork