Skaab Ruinator isn't a bad card as we're certainly likely to have cards in the graveyard due to manifest dread, but we're not likely to have that many early on, risking Skaab Ruinator being a dead card if it's drawn in your opening hand
Running more increases your chances of getting through, but going overboard with a thin proxy pool will hurt more than it helps
The deck is called Fluctuator for a reasonwithout it you are just kind of sitting around
All of these little, seemingly insignificant effects added up to Gitaxian Probe being one of the most powerful cards in the Modern format, which eventually led to its downfall
In commander, Elspeth most likely fits into superfriends archetypes where playing as many Magic: The Gathering planeswalkers as possible from War of the Spark or otherwise and using effects like Doubling Season and Atraxa, Praetors Voice to let them use their ultimate abilities early
Spellslinger Spellslinger decks are ones that focus heavily on casting non-creature spells, usually instants and sorceries