We've been getting the same type of apocalyptic analysis every December for the last 4 years or so.
The reports get more and more bleak until February 1st when Apple announce their income numbers and the share price goes through the roof.
This time around however, the reports started mid November instead, Apple has re-implemented Black Friday deals, and they are cutting prices in Japan and now supporting US sales.
Looks like for the first time ever, analysts could be onto something. The slowdown in the smartphone market is now catching up to Apple.
My only bit of non scientific input is that I manage IT buying for my company, and strangely, my supplier has run out of iPhone 8 last week. Looks like demand is indeed strong on the 8 versus the XR.
Finally if you want to trade-in a phone, there are tons of online vendors which will give you a lot more cash than Apple for these devices.