This answer is mostly sticking to the current canon and assuming cloning a force sensitive is possible (since the GAR was a clone army).
We could see this as a result of two things:-
1) Palpatine stopped the cloning process after the end of the clone wars and instead recruited normal people for his Imperial army. The reason behind this is expenses. Palpatine instead wanted to focus his credits on building his ultimate weapon, a death star.
I think it is fairly reasonable to agree that a death star is far more formidable and instills more fear in systems than maybe a bunch of force sensitives would have. Many people don't even know about or don't believe in the force (stated twice by two different characters in ANH).
2) (I think this one is far more important when we take only Palpatine into the picture and not the whole Empire).
Palpatine didn't really want many force senstives around. He had Vader to represent him almost everywhere. Note that the inquisitors were dispatched mainly to hunt down the remaining Jedi and potential Jedi, and would have probably been killed off by Palpatine after their use was over.
It is also important to note that Palpatine did face a problem with a clone in the past when his order 66 plan was almost ruined. Each clone has independent thinking and thus having more of these force sensitives increases the chance of one becoming hungry for more power and turning on the Emperor himself, after all, they too were dark side users (although not as strong as Vader or Maul).
I do have one possible reason (again for canon) about how cloning could not have worked. Since the clone army were clones of non force sensitives, maybe cloning might have been easier. However, there is a possibility that midichlorians interfere with the process or they cannot be cloned.
For the legends, I cannot be too sure. I mean Starkiller is a perfect example of how powerful a clone can be, but also strongly enforces my point number (2) about how a clone is an independent thinker and can turn on their master (although later in the game we do get to know that the cloning process has been perfected).