> use one version of their engine FOREVER

In an age of locked down mobile OSes and forever changing graphics drivers and such, I don't think "FOREVER" is very long any more.

It's like a perpetual license to a specific version of JetBrains Rider. It's sold as if I own a general purpose tool FOREVER and can opt out of an endless subscription but no, it doesn't mean much at all. It will not work with the next runtime update and past runtimes are obsoleted after a couple of years. They have managed to outsource their subscription lock-in as the release cycles of a third parties while pretending to be holier than thou. If they shipped the volatile parts as open source plug-ins, I would feel differently.