As RCS (Reaction Control System) mainly required less thrust than regular rocket engine can ion Thrusters be used for attitude determination in spacecraft(Orion, Dragon), satellites or even during propulsive landing of booster/first stages ?
Reaction Control System Thrusters typically have a thrust on the order of Newtons to tens of Newtons – hundreds of Newtons for atmospheric control (e.g. the RCS thrusters on Falcon 9 have about 400 N). Ion Thrusters in current use have a thrust on the order tens to hundreds of Millinewtons. There are experimental thrusters that have achieved 5 N in lab settings.
So, even the most powerful Ion Thrusters that aren't even in use yet are barely able to keep up with the least powerful RCS thrusters. If we are talking about typical thrusters that are actually flying right now, Ion Thrusters are off by a factor of 100×–1000×.
And that's only talking about RCS thrusters for low-mass vehicles in space. For sensible control authority within an atmosphere, as needed for e.g. Falcon 9, you need another couple of orders of magnitude.