As my teacher explained, whether we do or do not have freewill, when we drive the car, we must drive it well. Similarly, regardless of whether meditation is happening by itself, or "I" do it, it must be right meditation.
Practically speaking, we can control our mind, we can choose whether to get angry or to let go, whether to break through our phobias or to give in, whether to tolerate pain or to give up. This is our choice.
Similarly, we do have a choice of perspective: we can think we are sentient beings, having been born and destined to die, or we can generate the mind of nirvana. You always have choice, period.
Buddha was a huge opponent of the no-free-will-type theories with their tendency to take away motivation to strive for Enlightenment.
Now surely meditation is not about rigid control either. It's not about letting your mind run loose, nor is it about following an algorithm.
Enlightenment involves losing the form, true, but it also involves developing tremendous will power. These are the two legs we walk on the path.