Unlike the initial trailers for Black Panther, Thor: Ragnarok, or Avengers: Infinity War, the reception to the first trailer for Ant-Man and the Wasp one was decidedly more mixed across the board. The reasons for the reactions are varied; releasing the trailer the morning after glowing reactions to Black Panther feels admittedly silly, and some are still unhappy with the whole shakeout with Edgar Wright and the original film. One of the most popular ones complaints, however, seems to be how strange it is to release this film after Infinity War, though this film will have its events take place prior to Thanos' arrival to Earth.
To be honest, coming in hot off the heels of Infinity War may be the best course of action for this particular staple of the Marvel Cinematic Universe. Following up Age of Ultron in 2015 with the first Ant-Man film allowed for an outsider's perspective on the Avengers universe, succinctly explaining its existence with the fact that, to the larger world, a team of superheroes literally blew up a country just for the hell of it. With the exception of the Guardians of the Galaxy, every other corner exists in relation to the Avengers in some capacity.
Even though the first Ant-Man film contains Avengers by way of Falcon, it's a brief enough acknowledgement of the larger universe that could be cut and you wouldn't lose anything from the larger narrative. The original movie was originally designed as a standalone film before being integrated into the larger narrative of the world, after all.
Other MCU properties can't really afford this; Spider-Man exists because of the Avengers, Captain America's social circle is the Avengers, the Agents of S.H.I.E.L.D. and Defenders deal with the fallout of each respective Avengers movie, and Doctor Strange's area of expertise is a magical equivalent of the Earth's Mightiest Heroes. That refusal for superhero help is what allows Scott and the Pyms to carve out a smaller, but no less necessary and vital corner of the MCU.