Here is a sentence that I get mixed up. This is the beginning of the paragraph. There's nothing before this sentence.
'The types' of vacations that people take nowadays are very different from vacations taken in years gone by.
I think the the reason 'the types'(definite article) is used in the first part is to differenciate the types that exist nowadays and the types that used to be in years gone by. If that is the case, I have no idea why 'the' is omissed in second vacations.
Then, any differences were made if I put it like the following?
'The types' of vacations that people take nowadays are very different from the types of vacations taken in years gone by.