Answer why you believe God had to hide the truth from the people referenced in that scripture in order to prevent them from believing. Look at the context:
4 Again Jesus began to teach by the lake. The crowd that gathered around him was so large that he got into a boat and sat in it out on the lake, while all the people were along the shore at the water’s edge. 2 He taught them many things by parables, and in his teaching said: 3 “Listen! A farmer went out to sow his seed. 4 As he was scattering the seed, some fell along the path, and the birds came and ate it up. 5 Some fell on rocky places, where it did not have much soil. It sprang up quickly, because the soil was shallow. 6 But when the sun came up, the plants were scorched, and they withered because they had no root. 7 Other seed fell among thorns, which grew up and choked the plants, so that they did not bear grain. 8 Still other seed fell on good soil. It came up, grew and produced a crop, some multiplying thirty, some sixty, some a hundred times.”
9 Then Jesus said, “Whoever has ears to hear, let them hear.”
10 When he was alone, the Twelve and the others around him asked him about the parables. 11 He told them, “The secret of the kingdom of God has been given to you. But to those on the outside everything is said in parables 12 so that,
“‘they may be ever seeing but never perceiving,
and ever hearing but never understanding;
otherwise they might turn and be forgiven!’”
The critical verse is "Whoever has ears to hear, let them hear." So we're talking about two kinds of people - those with ears to hear, and those without ears to hear. And we also know that "Faith comes by hearing and hearing [comes by] the Word of Christ". Those on the outside didn't have ears to hear, but the word of Christ would give them hearing. It's not a matter of them having the capacity for truth.
The Bible is not written in parables. Jesus told parables. Time and place and the person of Jesus matter.