compatibility

Everyone is trying to get people to buy hardware, but I wouldn't say it's any kind of planned obsolescence on the part of Apple any more than Samsung or LG stops support.

But at a certain point all companies stop supporting older products. Computing advances especially quickly.

Before we sold my wife's iPhone 5, there was one more update that had to applied before a certain date, or it would no longer be able to communicate with any cellular service. If you're still using your 5s, then it's safe to assume you did this.

But you're talking about a 9 year old device, which for any make or model of computer is considered ancient. Worse for any cellphone since the hardware can't be upgraded, or pushed beyond a certain point of functionality with software updates.

As long as it still works for you, you can keep using it. But you have to also be aware the version of Safari on that phone is way behind on security updates and web standards in general. The version of iOS itself is also far behind on security updates.