Today i came across a sentence while reading a newspaper
"Half-yearly exams of secondary schools will be deferred due to closure of educational institutions"
But i think they were supposed to use "the" before closure like "the closure of educational institutions". Since it was talking about the closure resulted from coronavirus, it should be a definite thing.
If we try to refer to the dictionary, Wiktionary shows "closure" as being countable or uncountable. If "closure" is uncountable, then dropping the article as above is correct. But I believe that depends on which definition of "closure" we are talking about. From Wiktionary: "1. An event or occurrence that signifies an ending. 2. A feeling of completeness; the experience of an emotional conclusion, usually to a difficult period."
As far as I know, definition 1 is countable and definition 2 is uncountable. Definition 1: "There was a closure of schools." Definition 2: "He needed closure after an abrupt end to the school year."
So you are correct as far as standard English usage goes. But the fact that you were reading a newspaper tells us that this might not be standard English usage, but something called "headlinese".
Wikipedia defines headlinese as "an abbreviated form of news writing style used in newspaper headlines." One of the conventions of headlinese is dropping articles. It's not only found in newspaper headlines, but in lots of different places, such as titles of texts, announcements, and news reports.