Nokia 7.2 running slow with Android One version 9
There are some reports in Nokia Community that the most recent MR update (December 2nd update) release to the Nokia 7.2 has caused some lagginess for a number of users. You will need to wait for Nokia to push a release which fixes this. 

My Nokia 7.2 has been working normally. So, not all users are impacted. And some users already tried with a hard reset with zero luck.