When playing competitively, it is beneficial to players to have access to the same cards, and when looking at competitive Commander, its more akin to Vintage than it is to Modern
Necropotence decks ruled the day during the early stages of Standard, but the one card that even Necro players feared was Balance
Hexproof Primary: Blue Secondary: Green Tertiary: White Blue both has more creatures with hexproof and more often grants it as a pseudo-counterspell
Insidious Roots fits into decks like Teval, the Balanced Scale, The Necrobloom basically anything that uses the graveyard for value
Stardust Dragon X WIND Level 8 [ Dragon / SynchroEffect ] ATK 2500 DEF 2000 1 Tuner + 1+ non-Tuner monsters When a card or effect is activated that would destroy a card(s) on the field (Quick Effect): You can Tribute this card
Mirro-didn't Disappoint Even without Premodern to prop up these cards' values, the artifact delivered a ton of powerful gray-bordered cards that are worth a pretty penny today