The ability for good practices is already there, just too many people would rather complain about their bad practices to bother learning the good practices and blame the language.
1. I require more of an explanation as to what you mean by decrease scope. I could interpret that in different ways.
2. Sure, I understand the discipline necessary to prevent that is difficult in a team setting. I would say that likely at reaching that point something went wrong before then. That seems a tooling problem, not a language problem. How many languages provide features out-of-the-box that assist with discovering unused code without some form of third-party exploring that space?
3. In what way? What scope problems? I can think of several bad practices that lead to scope problems. I can think of examples of two people following two different best practices creating such problems.
4. I know it's not exactly a fair thing to say, but I don't have those issues with the example you provide. I'm sure there's plenty of examples of showing how to do it.
5. Flex. But, granted, old practices didn't handle vertical issues well because originally HTML wasn't intended for that.
6. In what way? Do you mean variables from a pre-processor or CSS custom properties?
I'm sure there are more, just like almost all languages have their quirks and issues that make it difficult to address if not understood. Do you have any other examples that we could discuss? Are there any specific use cases where you are having difficulties that I might be able to help out with?
If the language were better, they would have learned the good practices while they learned the language, and they wouldn't even be able to express bad practices without extra effort.
