Why is Windows 10 Bluetooth so so so bad ?

I hope you enjoyed the wasted time calling the manufacturers and the time spent on the configuration which was supposed to be a trivial task...

Just like on a mobile phone, after buying a high-end laptop you expect it to work out of the box. You try 4 different headphones and you have a terrible result in all cases. You try the same headphones with a mobile phone and then you try with other platforms. You realize that outside the Windows they work flawlessly and you come to the conclusion that it is yet another day with M$ solutions. 

And it's not a unique situation. Most of the people I have talked about it have the same experience.

A little problem with your diatribe: Bluetooth works flawlessly on my copy of Windows 10.

I just had to learn how to use it.

As a 20 year Windows user, I can tell that you have no idea what you are talking about.

• yes, we know that BT protocol is a mess 
• you can take whichever phone you like - most expensive apple phones or the cheapest Android phones you can find on the market - they will work more or less flawlessly. The range is great! It automatically switches between the call and music(?) modes without user intervention. The quality is good. ...and they are working with the same protocol and somehow managed it to work great!!! 
• Nothing from it you will find on Windows - just google the BT horror stories on Win.
• As I already wrote, I've tested the same hardware on Win 10 with Intel drivers and on Ubuntu with some generic drivers and it is like comparing a bicycle to a Ferrari.
• I've spent two days troubleshooting why on my Windows it is not possible to get the audio and mic functionality AT THE SAME TIME. I can get one of them to work, but if I've selected Handsfree mode for audio AND mic, only one will work. I know that there are some lucky people who have this working, but after searching countless forums, testing many drivers and various BS Win settings, this is yet another day where good old clean Win install is required. (On my work PC I need to do that around 3x a year after some Win updates it gets to a state, where even my guru coworker who used to be an MS sysadmin, gives up)
• last but not least - the user interface! If I need to troubleshoot why again my audio/BT is not working, from the Desktop I will open the corresponding menu (the new UI which in best M$ traditions will only include 5% of the functionality) and if I actually need to fix something, I have to find one of 1000 links on that UI which will open the old config panel, where the actual configuration can be done.
• This also explains why everything that MS migrated to the new UI is a disaster. The Mail app, the UI, the Appstore support, we can go on forever. They migrated 20% and called it a day. Visually I think the new look is good, I like the minimalistic design, bet the UX is beyond frustrating. 

"I've yet to come across a more drastic failure by a technology company than this. Period. Beyond frustrating." - 100%

I've yet to come across a more drastic failure by a technology company than this. Period. Beyond frustrating.

What's "beyond frustrating" is actually the Bluetooth part, not the Windows part. The Windows part is drop-dead easy.

This is the Windows part: Your PC either shipped with a Bluetooth adapter (i.e., installed by the factory) or it did not. If it did not, you can buy a Bluetooth adapter (aka Bluetooth dongle) and plug it into a USB port on the computer.

If your PC shipped with a Bluetooth adapter, the manufacturer installed the driver at the factory. If you bought an adapter, the driver either came in the box or (more likely) you downloaded it from the manufacturer's website and installed it yourself.

Now, all you have to do is to go into the Settings app and turn the Bluetooth adapter on. Ta da, you're done. Presuming that you're not the type who messes around in Device Manager, the Windows registry or other internal settings, you've done everything you need to do to get Bluetooth up and running on Windows. That was easy!

Now we come to the frustrating part: dealing with the Bluetooth technology, which is completely separate from Windows. Here's where you need to deal with pairing and connecting, master and slave, multi-point and choosing profiles. And if you think that all Bluetooth headphones or earbuds or keyboards, etc. work the same way ... guess what? You'll need to do a lot of hit and miss and phone calls to the Bluetooth device's manufacturer before you finally get your device to work properly and reliably.

It shouldn't be that hard. But to make everything easier, competing hardware manufacturers would have to actually cooperate to synchronize their technologies. Like that's gonna happen. Do you remember the frustration that came with burning CDs years ago? Bluetooth is not any better.

Bluetooth devices can work great, but to get there you have to come up with the proper settings and sequences of how you use the devices and then do not change a thing - nothing.

I've yet to come across a more drastic failure by a technology company than this. Period. Beyond frustrating.