Pauper is a community-created MTG format that limits deckbuilding to common rarity only, making all uncommon, rare, and mythic cards illegal in structured play
By playing enough of both, you'll be passively gaining lore, draining your opponent, and have a board state that will be very tricky for your opponent to unpick in time
Just because Historic decks cannot cast a Brainstorm on Turn 2, fetch, then play a Thoughtseize with their second mana, does not make it weak
In my experience it is often inevitable that a Heliod deck will be able to put one of their combos together, and it might be better to hold instant removal back to break up whatever version they end up finding, lest you waste it early on a redundant or superfluous creature