Later in the game, if you cast it for the full 5-mana creature, you get up to a 5-mana permanent back
While the Knight creature type has been around since some of the earliest days of Magic, more recent sets including Throne of Eldraine, Ixalan, and Dominaria have added many new cards to the Knight card pool
There are enough non-creature threats in the Commander format that can make Filter Out a strong inclusion, especially if it offers your strategy a lot of value
It can swarm the battlefield with Urza's effect and turn all your artifacts into mana dorks to pay for both Urza and various spells easily
This rare red card is still plenty cheap, but it has doubled in value since the latest set, Aetherdrift, came out, and still seems to be climbing