There are only so many measurements we can take from Earth or Earth orbit regarding the nature of the cosmos. It's a big universe, and we might need a space probe sitting at the edge of the Oort cloud (between our star and the nearest like Alpha Centauri) before we can get accurate readings.

Fact is that it's remarkable our scientists have been able to puzzle so much out on our universe sitting underneath our planet's murky atmosphere and intense magnetic fields. We truly need to be an interstellar civilization before we can start getting data on where the "missing" matter of the universe is. It simply means we need to venture out further into space before our readings can deliver more accurate results.

Trying to figure out the precise nature of the universe using 21st century technology located on Earth is like trying to observe a solar eclipse in a thunderstorm.