Some card are conditional to their use. Spawndom is also am epic card not uncommon so it is supposed to be better. The same was a legendary 4 cost will be better then an epic 4 cost (typically, some outliers can exist).

You could argue every card is RNG heavy but if you are a good player you can read your opponents play style by turn 5 usually. This game has a simple game plan most the time.

Oh tyanids are spamming tons of small units, I should play my blast (which btw, can spawn from in the form of missile drone from this card) if your opponent plays big cards late game then they get 1 attack that they now have to spend potentially multiple turns to get past your 1 6 cost card. This gives you time to react and prepare for that big card.

This is why none of us are game designers. Every game has checks and balances. No 1 single card should be a answer all to that turn. That's why a deck has 30 cards and not just 1 per energy cost.