Some color combinations simply dont have any mana ramp worth playing at all, either forcing you to consider extremely mediocre options or exclusively rely on single color cards and mana rocks to get the job done: Dimir (Blue/Black) Boros (Red/White) Orzhov (Black/White) Esper (Black/Blue/White) Grixis (Blue/Black/Red) Abzan (Green/Black/White) Sultai (Black/Green/Blue) Temur (Green/Blue/Red) Most 4-color groupings That doesnt mean all other color combinations have amazing ramp options though many can only offer situationally powerful cards
Skithiryx, the Blight Dragon ( F, C, LC ) - A 4/4 infect for 4, that you can give haste and regeneration
Frantic Search is currently banned in Legacy and Pauper
Collector Boosters guarantee 5+ cards of rare or higher rarity plus premium finishes like foil-etched, textured foil, and borderless variants
All that said, deck optimization isn't a priority for many casual players, and there's still plenty of room during deckbuilding for a flexible 3-mana spot removal spell.