It's like this with T-mobile, and many other retailers. I've heard others echo your findings. Basic and flip phones are a very small market now, and they are of terrible quality.
When my old Nokia 3390 started to give up about a year ago, I found a used iPhone SE model, and got used to it. As I understand it, there aren't any quality basic phones still made.
That being said, there are industrial-type flip phones that are still of good quality, if you are willing to pay. Here's a Verizon example, on Amazon.com (I shortened the URL):
formatting link