Personally, I'm hopeful for this and think it could be good, or at least one of the better in-franchise Exorcist films (which isn't a very high bar). On its surface, Exorcist: Believer does seem like a generic legacy sequel that ticks all the usual legacy sequel boxes, but it all comes down to execution.
Other than the incredible and iconic original film, I also love The Exorcist III and I think it was a very worthy and unique follow up to the original. It thankfully ignored the garbage Heretic sequel. And while interesting to watch the two versions of the prequel film (The Beginning/Dominion) to see the differences, neither of them were any good.
The TV series, however, was surprisingly very good and proved that there is still some life in this original franchise if handled correctly. Really wish that series has gone on longer.