Sorry to hear your experience. Next time you'd be better off buying from a more established brand if you going to buy a phone of Chinese brand. Chances are, if they are officially selling outside China, they would have met some the requirements from the respective countries. I know Europe and US has strict privacy laws and that's why you can't buy such phones through official channels.
That seems rather pessimistic. If you really don't trust any brands, what's wrong with directly buying from the tech companies instead of the manufacturers? Like Google Nexus (Pixel), Microsoft Windows Phone and iPhone. They are supposed to the industrial standards for how to do privacy correctly.
When a simple Google search reveals the exact pattern mentioned occurring again and again, not just with phones but with networking gear, laptops, TV's, IoT devices, CDs (Sony rootkit anyone?), and websites loaded to the max with trackers and secret downloads onto people's machines, it moves from pessimism to "this is just how it works."
The price of freedom is eternal vigilance. You want crap free gadgets, make them sell crap free gadgets by ratting them out when they sell gadgets loaded with crap.
What standards are you talking about? I don't know of any. AFAIK, the standard is to monitor users and collect as much data on them as possible. The whole Internet runs on that model.
The market could be driving that. If you don't spy on a user then your competitor would do and get ahead of you (and get additional profit from selling the data or showing relevant advertisement).
Microsoft didn't have any telemetry in earlier days. Now they turned to a dark side.
Even if I bought a Samsung (that is established brand, isn't it) or Apple phone I still would have to trust the manufacturer that it would not spy on me even if requested by NSA. I know that Samsung adds additional software into Android, they might have some kind of analytics too.
