ETERNALS was never meant to be a sure "blockbuster." All indications point to Marvel/MCU/Kevin Feige overloading Eternals for the purpose of being a key movie to reference in the MCU future as it will be a SIGNIFICANT movie to Phase 4-5.
The story of the MCU Celestials-Eternals-Deviants opens up the cosmic storyline with Galactus/Silver Surfer, Adam Warlock, Abstract Entities, and possibly FF, mutants, and - yes - Infinity Stones origin.
Fiege is a brilliant Master Psychological Strategist. He is a phenomenon beyond the best of Hollywood producers. Expect 100+ of Easter eggs imbedded in Eternals that will hatch in upcoming MCU and add lore to previous MCU. I have learned NEVER to underestimate "FIEGIOLOGY" long-term cohesive focus imbedded in each MCU movie and TV shows.