A lot of the software that makes JavaScript web development possible is C or C++, like web servers, databases, operating systems, network devices.

Composition is far better and immensely more flexible than inheritance. Extracting duplicate code into helper classes or static functions is a good option.

Conformance to interfaces or protocols with default implementations is a great alternative as well.

I like OOP more than other styles, it’s just often badly done. Complex inheritance, huge classes that do too much, overuse of factories and similar patterns, can ruin it.

Yes, it targets old operating systems. Old browsers don’t have the right certificates installed, nor do they support current encryption algorithms and protocols.

If you ever need a search engine without JavaScript or https, give http://frogfind.com/ a try. Works great on ancient browsers and operating systems.