Why are people questioning continuity in a deadpool movie
Why aren't they? We wouldn't be having this conversation if First Class hadn't contradicted the original trilogy or Origins: Wolverine. Even when Days of Future Past changed the timeline, the continuity is still screwed up by messing up some of the characters' ages, skin color, etc. such as:
-William Stryker (in Vietnam): older in Origins, younger in DOFP.
-Bolivar Trask: tall black man in X3, white hobbit in DOFP.
-Emma Frost: teenager in Origins, adult in First Class.
-Moira McTaggart: Young woman in X3, Young woman in First Class.
-Angel: kid in 90's flashback and adult in X3, teenager in Apocalypse.
-Jubilee: teenager in all 3 X-men films, teenager in Apocalypse.
As for Deadpool, he may be a different character from the one in Origins but the movie is most likely set in the new future ending of DOFP with Colossus as an adult and Negasonic Teenage Warhead texting before she tackles Angel Dust.