I feel your pain. I have the same in my 2017 i3.
I think German cars in general don't do as good of a job with air conditioning as American cars. The Germans, until recently, were never fans of air conditioning (not a pun) and it was rare to find an office building or home in Germany which was air conditioned. The Germans created great window technology, huge ones which opened out and up, and were super energy efficient for the winter. But they never got air conditioning.
My wife's BMW X3 has the same problem too. Her AC is awful. When she brought it in several times for service, the service advisor said that's the way these cars are.
So for both the i3 and x3, there are three things you can do to improve the AC (at least this works for us):
- Max AC always gives a good blast of cold air, so I start out with Max AC. But in my car at least, it's too cold so I can't leave it on too long.
- when the temperature is comfortable, go from Max AC to Auto, but turn the recirc button the 'M'
- in Auto, turn the fan up by a few notches. I have it one notch below max.
This is what I've been doing for the last week in 95+ degree F temps as I've been commuting in traffic. And the comfort has been perfectly fine.