Agents Of S.H.I.E.L.D. - 10 Things You May Have Missed In The Series Finale
3. A Separate Timeline
Right, here's where things get confusing. Upon returning to their "original" timeline, there are enough discrepancies to safely assume that Agents of S.H.I.E.L.D. does not, and never has, taken place in the Marvel Cinematic Universe fans see in movies like Avengers: Endgame and Black Widow, as well as upcoming Disney+ TV shows like The Falcon and The Winter Soldier and WandaVision.
This timeline is just too different; the 2020 they land in is one of hope and prosperity, and not the desolate world that was left in the wake of Thanos' attack in Avengers: Infinity War. There's no indication that the "Snap" (or "Blip") ever happened, and it makes zero sense for this newly created S.H.I.E.L.D. not to have been part of that massive battle against Thanos in 2024.
Agents of S.H.I.E.L.D. hasn't really tied into the movies since Captain America: The Winter Soldier way back in 2014, so this isn't a surprise, but it does offer confirmation (of a sort) that all the "Marvel Television" shows were set in their own pocket universe completely unrelated to the MCU itself.