That's some really nice board wipe and spot removal protection
Entering with six whole loyalty counters, plus a passive ability to generate advantage, plus threatening removal and it makes its own blockers
Although Mew is canonically stronger than Mewtwo, Mewtwo is a powerful force, and when the base set was released, this card was often used in play, making it much rarer to find it now in good condition
Throw it on a flying 3/3 and that's often an overperformer in my decks
And yeah, turns out Impmon was always a bit of a bookworm
From the Deva Arc onward, the Blue Cards' primary use is enabling the main Digimon Partners to reach their respective Ultimate-level forms, WarGrowlmon, Rapidmon, and Taomon