This verse is frequently interpreted as a command—or at least used to justify a certain course of action—but the plain fact is that it is a prophecy. It is a statement of a definitive future event, rather than an instruction.
Consider for a moment what this prophecy does not say. There is no mention, either in the verse or in its context, of who will have done this preaching. It does not say whether one individual will preach it or two individuals, one organization, seven organizations, or an angel. This verse just says it will be done.
Matthew 24:14 also does not tell us the time involved in preaching the gospel, except to say that it happens before the end. It does not indicate whether it is preached over the course of several decades, or whether it takes 42 months, or whether there is a singular announcement that all the world hears at the same time through some form of mass media.
This verse also says nothing about how this preaching will be accomplished. There is no mention of television stations, radio programs, websites, Internet streams, or any other technology. The verse simply says that it will be done. Only God knows exactly how it will be fulfilled.