So the point of this device is, and I had that thought when it was announced, if you want good mid-range Xiaomi go for the Redmi Note 5 Global/China variant as it's better in every aspect (except the GPU, camera software does give an advantage to A2, however hardware wise RN5 has more potential), and if you want a more premium looking device with close to stock Android go for Nokia 7 Plus (better main camera as well + battery). - this is advice for the people who want to use the device as it is.
If someone wants to use the device with custom rom (+root of course), the best choice would be the RN5. I am using one with AOSP based rom + custom kernel (UC/OC) and have a modded Google camera running, the picture quality is on par with Galaxy S8 indoor with artificial lightning (low/medium lightning conditions) and in some situations it surpasses it, I've done a side by side comparison with a friend last night. That's possible because the phone is using the same DSP and ISP as in Snapdragon 820.
Most of the "advantages" that some pricier phones have compared to more budget friendly devices (in the Xiaomi lineup) are software based, hardware components are similar if not the same, they are just being held up by software to differentiate low/mid/high end devices.
With these cons, it is just better to get the 6GB variant of Zenfone Max Pro M1 which comes with better cameras, same Android One experience at a LOWER price than Mi A2 despite having a Snapdragon 636 so long as one does not play many heavy games often. Or better still, stick with Mi A1 if you still have it due to poor battery life on Mi A2.
Uninspiring battery life
Dim display, unimpressive sunlight legibility
No headphone jack
No microsd slot
There, fixed it for you.