That is why you didn’t see anything from Solo: A Star Wars Story before The Last Jedi released or Rogue One before The Force Awakens.
Avengers: Infinity War is the biggest Marvel movie ever, so it is unsurprising that the studio is doing it’s best not to shortchange it by letting the focus shift to what’s next.
Despite that, with this franchise, perhaps more so than any other save Star Wars, secrecy of any kind breeds speculation and hype.
With Marvel having announced its slate, that does make things trickier, but you still don’t see much from a film until it’s the next in line for release.