If you try to build an app today utilizing those features without using modern tools you’ll quickly learn why those tools were created in the first place. They’re there to help solve a set of very complex problems, and without them you’ll find yourself struggling to manage all that complexity manually.
And they manage to avoid the framework fatigue and choice paralysis found in the JS framework landscape. I personally use Amber Smalltalk and I love it.
You can deny it all you want, but these transpiled languages are perfectly modern tools.