I find most constructed (modern and legacy) creatures tend to underperform in cube since they are either combo pieces or undercosted beaters that come w deck building restrictions to fully take advantage of
Creatures cant be cast or enter the battlefield
Even if your Gollum is destroyed or enters the graveyard for any reason, you can bring it back to your hand for a relatively small cost
Commander is the single biggest driver of prices in Magic at this point
Take advantage of discarding strong cards like Sire of Seven Deaths, Koma, Cosmos Serpent, and Valgavoth, Terror Eater
This makes sense, since both sets were the first time back on planes which had pretty underpowered sets the first time around, so perhaps were righting the historical balance at WotC