I would say yes, it is a solid upgrade. 90$ trade-in value for the Air2 is a good deal and the iPad 2021 9gen will run circle around the Air2 in terms of performance.
The screen is slightly larger, but downside is that it is non-laminated and have not received the reflective coating found on the Air. Some people will consider these factors a dealbreaker but I would personally consider them minor compared to the performance upgrade and ability to use a proper stylus (Great one can be found cheap on Amazon). Plus, you just don’t get anything better at this price point.