It seems to be a contradiction: an award seat is becoming difficult to find in a time when frequent-flier miles are more easily obtainable than at any time in aviation history.
After all, you can earn miles flying, staying in hotels, buying paint to finish your recreation room or food for your cat. You can also learn to manage those frequent-flier miles.
Financially struggling airlines don't like to give up free tickets on certain routes. Perhaps the airline with which you have accumulated mileage riches doesn't fly to your next desired destination.
Why not shop that airline's alliances?
In other words, many major airlines share services with comparable airlines in other countries or on other continents. That largely domestic carrier won't get you to Paris, but perhaps their alliance partner will accept the miles and save you an award seat.
Next step: What's the best gateway to these complex webs of travel opportunities?