While Thor and Hulk weren't featured in Captain America: Civil War, and with Thor: Ragnarok being set in space, that doesn't mean it's not connected to the greater Marvel Cinematic Universe.
Director Taika Waititi does state his Thor: Ragnarok "can sit as a standalone piece," but at the same time Chris Hemsworth teases it connects to The Avengers: Infinity War.
“We didn’t want to get bogged down in Infinity Stones and da-da-da-da because I don’t even understand that stuff a lot of the time…” Chris Hemsworth laughed as he told Collider during a set visit, “[But] I spoke to The Russos before I even had the script for this and said, ‘How does [Thor: Ragnarok] link into [Avengers: Infinity War]? What can we look out for? How do we continue this time?’… Without giving anything away though, [Thor: Ragnarok] definitely bleeds nicely into those [films].”
Regarding not wating to giving things away, the Avengers: Infinity War trailer might offer why.
Thor: Raganarok has a November 3, 2017 release directed by Taika Waititi starring Chris Hemsworth as Thor, Mark Ruffalo as Hulk/Banner, Tom Hiddleston as Loki, Idris Elba as Heimdall, Cate Blanchett as Hela, Tessa Thompson as Valkyrie, Jeff Goldblum as Grandmaster, Anthony Hopkins as Odin and Sam Neill in an unknown role.
Thor's world is about to explode in Marvel's Thor: Ragnarok. His devious brother, Loki, has taken over Asgard, the powerful Hela has emerged to steal the throne for herself and Thor is imprisoned on the other side of the universe. To escape captivity and save his home from imminent destruction, Thor must first win a deadly alien contest by defeating his former ally and fellow Avengers... The Incredible Hulk!