Definite articles_plural and uncontable nouns_generalization

Question

I am learning about definite articles. I came across a thread: Definite article: "use ‘the’ with names" vs "use ‘the’ with the names"

That says "the" is optional in these general sentences below:

[The] leaders of democratic nations are usually persuasive public speakers.
[The] shorelines of lakes are sometimes highly developed.
[The] covers of graphic novels often feature a dramatic scene from the story.

If so, when talking about a type of something in general, I can use either version. Right? Could you tell me the subtle difference between the version with "the" and without "the" of sentences above?

As I can see, the examples above talks about plural noun (leaders, shorelines, covers, . I also wonder if this can applies with uncountable noun when making a general statement. Is "the" also optional in these sentence below:

1. (The) development of cities has become the first concern for governments in the word.

2. (The) contamination of water has become severe nowadays.

Answer 1

I prefer "The development of cities has become ...", but "City development has become..."

I don't think it is an error to omit the in "Development of cities has become..." But the sentence seems more fluent with it, perhaps because "of cities" specifies a particular type of development.

And not "The city development", since this article seems to refer to a determined city, not a determined type of development.