I hate to discredit a Hall of Famer, but I came across this quote from Hakeem Olajuwon in LZ Granderson's otherwise wonderful story about the rarity of quadruple-doubles in the NBA:
"When I was playing, it was expected that a good player, especially a big man, would get a double-double. Today, getting a double-double is considered special."
Hakeem Olajuwon's career double-doubles (data only from 1986-87 season): 674
Average per 82-game season: 53
Double-double leaders, last four seasons: 69, 66, 62, 69
Number of players who compiled 53 or more double-doubles, last four seasons: 4, 3, 4, 2
Even giving credit to Olajuwon due to the fact those numbers encapsulate the decline phase of his career, and while it may be true that the number of players achieving double-doubles were greater "back in the day," it would seem pretty obvious that double-doubles by the elite players are as frequent now as they were back in the day.
And, of course, none of this takes into account pace or number of possessions.