When you’re choosing the instrument to add in Dorico, pick carefully - for instruments that have multiple possibilities, those possibilities are typically listed separately.
If you’re dealing with pre-built ensembles, or opening someone else’s file, or importing in MusicXML, pop open the Player in the left panel of Setup mode, click the three dots and then go Edit Instrument Definition.
Scroll down to the Transposition and take a look at what’s defined there.
If it’s wrong, change it.
There’s no need for guesswork, here.
For what it’s worth, if what you always want is a C score that shows all instruments at sounding pitch, including double basses and glockenspiels, feel free to change it here in the Written middle C (note 60) sounds as: section. Part Layouts in Dorico are, by default, always Transposed (even those of C instruments), so this won’t affect the Part Layouts. Just don’t put such a score in front of a conductor!