> The donkey still is important for legacy runtimes, which probably have many decades of lifespan left.

Yep you're quite right, and actually the fast-moving, high-churn transition to .NET Core has been tough on devs still working with (now) "legacy" .NET Framework apps - which as you say, will have many years of lifespan remaining if they still fit the purpose for which they were built.

I don't envy those devs (and I do still have some legacy Framework stuff that I provide support for - but not for too much longer thankfully).

It is a little frustrating seeing how quickly so many libraries, even first-party Microsoft ones, have ditched support for dotnet 4.8.

There's an entire universe of enterprise stuff that hasn't caught up, or relies on features that have been dropped from future dotnet Core/5/6+ support.

We still have plenty of COBOL developers maintaining and upgrading legacy applications. Framework, and all the apps running on it, are officially legacy now. Legacy development has entirely different challenges and limitations to modern development.