.NET only became open very recently, it's been quite successful. The entire iOS/Apple developer ecosystem is closed source of course. Maybe Swift isn't but nobody uses it outside the Apple platform.
You could argue Microsoft is an exception and them opening .NET shows the end of that era though.
The "open source or nothing" mentality might change in future. It means there's not much market for developer tools, so everything gets hacked together out of random "frameworks" found on GitHub that are here today, gone tomorrow when the bored developer at Netflix or Google gets their desired promo and moves on. There's no real planning or design, just whatever random stuff tech firms throw in the mix as a side effect of other projects, which is why HTML has virtual reality support but no table or spreadsheet view worth a damn.