Watchtower uses two scriptures that I know of to apply things to today.
-- "For all the things that were written aforetime were written for our instruction, that through our endurance and through the comfort from the Scriptures we might have hope." (Rom 15:4)
-- "Now these things went on befalling them as examples, and they were written for a warning to us upon whom the ends of the systems of things have arrived." (1 Cor 10:11)
Of course neither of these scriptures say anything about applying to today, but to the time they were written, 2000 yrs ago.
The Society makes an application of them by extension, bringing them to our day.