That's a problem, not an issue. Why are you afraid to use direct words?
There are two perspectives, here. One is, "My devices have worked together for years. They stopped working as they used to. Why, and how can I fix it?" Both perfectly reasonable questions. A next question might be, "What changed, and why?" Also a reasonable question, but not one that always has a single, simple answer.
Another perspective is that technological devices are complex and ever-changing. This is due to a lot of reasons, like the desire to add new features and incorporate new technologies, the need to continuously fix security issues that arise from continuously changing the hardware and software, the need to create and market new & more exciting devices to consumers, etc. You may not want to spend the time to fully understand the technical details of the answer. In that case, you'll have to accept someone else's advice when they say that you need to simply accept that phones change rapidly, and the easiest & cheapest thing to do is to adjust your
expectations.
New features & methods are always being created. If those features & methods are adopted by phone makers, they eventually become standardized. When your phone was released in 2014, an older version of Bluetooth was in use. Older, very different versions of Android were in use.
It would be impossible for every device manufacturer to perpetually find and fix every compatibility issue with every new version of Android with every one of their devices. That's why phone makers have "end of support" dates. It doesn't mean that your phone suddenly stops working, it means that that's the point at which they stop fixing problems that come from using the device with new wifi protocols, new cellular standards, new versions of apps, new versions of Android, Bluetooth, etc. etc. etc.
So what changed with your car and your phone? Beats me, but one possibility is that one or other had -something- that updated, somehow. Or, it could be that something broke. (Have you tried other phones, yourself? Have you tried using your phone's mic with other devices besides your car?) It is possible to track down the cause of the problem, but it isn't feasible for a business to do that for you without charging you a lot of money for the expert labor involved. Your problem could cost many thousands of dollars to identify, and there's no guarantee that it _is_ fixable. (For example, some vendors have locked bootloaders and crytographically validated firmware updates, and they may forbid downgrades. There are reasons for doing that, too.)
Short answer: trust us when we say, "It may be fixable, but it isn't rational to attempt it. It would cost a LOT less to simply get a newer phone that supports current Bluetooth profiles and protocols." If your new (or newer) phone has the same problem, then you'll know that something broke. Otherwise, your phone is old, and no company can possibly support every version of everything, going back years.
I know it's frustrating, and it may feel like a conspiracy against you, but it isn't. (Usually.) Constant updates are unnecessary (and mostly undesirable) when it comes to simple machines. With complex, interrelated systems of many, many devices, all communicating in a variety of ways... you simply have to adapt.
You could buy a still-supported used phone, if you wanted, but be aware that by buying a three year-old phone to replace your six year-old phone, you may not get six years of trouble-free use out of it. Your carrier should tell which devices they support. Grab something newer. In the mean time, have your friends test out media & phone stuff. That'll let you see that other devices may work differently.
I hope you found my response to be direct. Remember, the fact that you're frustrated by the situation isn't evidence that people are trying to bamboozle you. I'm not. I have absolutely no stake in whether you get a new phone or not.
