While i do agree a bit, I think a lot of that was because we were so "Wowed" by the first Deadpool. Similar to Avengers and Avengers Age of Ultron. Same team and Avengers Age of Ultron wasnt by any means a BAD movie, but we lost that magic of seeing all of it on screen for the first time. Definitely had highlights though. Im probably doing horrible at explaining what im trying to articulate but hopefully you have an idea of what i mean haha.
I do also agree with you though that Deadpool 2 did get a bit stale in parts. So maybe you're right, a change of writers might breathe some new life into it. My main concern is being with a different team, maybe that means Marvel Studios is trying to tone the franchise down as theres been rumors back and forth since the purchase that disney wants it toned down, but then rumors will pop up that they want deadpool to continue as is.