I did a Flex/AIR project a few years ago. At the time, it was a customer requirement. They had fired their previous provider, because their business model was to charge a subscription fee for the server-based product.

All their "media" was in flash format; so they made it a requirement, even though they could have saved themselves many tens of thousands of dollars in hardware costs by going to a mobile platform. (they did not have reliable access to networking in most of their deployments, and didn't want to bear the costs of rolling their own with cellular).

So I wrote the app in a "AIR isolated thick client" mode.
There were many problems with garbage collection and application freezes, that could have been addressed had they funded migration to post-Adobe FLEX (Apache FLEX). But they ran out of funds for that.

Their platform was Win 7 laptops. The first hardware iteration was fine. The next year, when they started replacing the laptops, they hit a driver bug that caused the whole screen to freeze. With the next hardware iteration they were able to fix that, but they started having problems with AIR trying to download an update when they were not connected to a network (ie. deployed in the field). AIR behaved badly in this instance and refused to run.

When they moved to Windows 10, Adobe hadn't updated the AIR player yet, so they had another botched deployment.

It was in our contract to hand over the source code, so they tried to hire their own developer. I spent many hours very thoroughly documenting the code, and they had no hours budgeted for ongoing support. Judging by some of the desperate emails I was getting last year, before my Program Manager told them to fuck off, I think my documentation was not enough. Of course: the Dev Environment setup was Win 7, Eclipse 3.x with the Adobe plugin. I maintain a VM of the dev environment, but I doubt even I could follow my own directions to set it up anymore since the Adobe SDK of that version is so difficult to locate.

Had they listened to my original recommendation to write the entire application in Java, they would still be running fine.

That was my most recent experience with "death by technical debt".

Many years ago; a product died simply because a competitor bought our company, and tried to sell both products (because theirs was a "consumer market product", and ours was "enterprise market"). Over the next 18 months, they cut development to the enterprise product, and tried to tart-up the consumer product to meet the needs of our enterprise customers. I was a major account manager, so I watched one by one as our frustrated customers dumped everything our company sold, and went to the other competitor. So that product wasn't so much killed by technical debt as it was killed by moron MBA's.

In the end; all of those products are obsolete because nobody used dedicated backup tape library software anymore. It became a very small market because tape backup hardware never got commoditized, and prices just never came down from "insane". Even blank tapes were more expensive than a removable hard drive. Poor people just back up to the cloud, pay rent to someone else for their own data, and end up losing it.

I can probably think of about a dozen other examples from my long and miserable career in software.