Q. The two parables from this passage promise the growth of the kingdom, but what about all the places in the New Testament that talk about how bad things will be at the end times?
A. When New Testament authors use the phrases "the last days," "end times," "last hour," "end of the age," and more they are referring to their own situation. Paul says in Hebrews that "in these last days God has spoken to us through his Son" (Heb. 1:2). John says, "it is the last hour" (1 John 2:18-19). They are talking about the end of human history in some distant future. Rather, they are talking about what is happening right then and there. What's coming to an end in their lifetime is the old age or the "old covenant." And it is ending as God brings judgment, specifically the judgment coming on the apostate Jews and Jerusalem. The church needed to know that the old age with its Jewish-centered world, sacrifices, food laws, a central sanctuary, etc.–all of that was ending in judgment. The work of Jesus ushered in a new age and therefore ended the old age.
Paul warns Timothy: "But understand this, that in the last days there will come times of difficulty. For people will be lovers of self, lovers of money. . ." (2 Tim. 3:1). He's not talking about something that will happen in the 21st century or at the end of human history. He's talking about what is going on in the world that Timothy and his congregation inhabited. And the evidence is all over New Testament history that as the church grew in faith and love, the apostate Jews grew more violent and hateful in their zealotry. After 40 years of grace and multiple opportunities to repent, the Lord came in judgment in AD 70.
So the bottom line is this: When Jesus and the Apostles predict evil, suffering, and tribulation for the last days they are referring to their own time and situation. They were living in the "last days" of the old world. Once Jerusalem and the apostate Jews are judged, the kingdom expands and grows.
I've used this chart before. Perhaps it will help.