So your saying the blame is on the producer? I think that this is clearly getting off topic..
To answer the original question, you can either make your beat louder by providing a loud mix.. or
it can be raised through mastering.. which in the process of mastering (the instrumental) will
boost the volume somewhat.
That's My opinion.
As far as I know, Producers who sell their beats online, sell either the mastered beat, or the unmastered beat. All depends on the preference of the producer. If the artist has problems, they can contact the producer (which they do) asking for project files, or asking for changes to be made..
This is the Nature of the Business.. Hope this answers the initial question.