I don't think anyone is saying Orr is bad. But I definitely think its reasonable to think his loss isn't extremely significant. He excelled as a run-stopping linebacker- which are about a dime a dozen in today's NFL. Despite the interceptions he had, he struggled a lot in pass coverage (not a PFF fan- but they did have him as the second worst linebacker in coverage in the NFL last season). I wouldn't characterize him as a weak spot on the defense by any means, but he could definitely have been considered a limited player despite playing a 3 down role.
We won't know for a couple months whether Correa has the mental part of the game down or not, but as a physical specimen Correa probably brings a lot more to the table than Orr.
So are there questions? Obviously, but every team deals with losing players and having to replace them.
Would Orr be starting if he were still in Baltimore? Probably.
Is the defense worse without Orr? Maybe, but probably not significantly worse. I'm happier that the team spent the money to go after Jefferson and Carr than have brought Orr in for what probably would have been his last season in Baltimore anyway.