Yes, it is okay for Christians to meet in large buildings instead of house churches. Likewise, it is okay to meet in house churches instead of large buildings. The reason the early church met in house churches was that they didn't have large buildings in which to meet. The synagogues were for the Jews, and the Jews were not favorably inclined with the Christians. Remember, the Jewish religious leaders killed Jesus, so His followers weren’t going to be treated well. So, Christians met where they could, which was in homes.
- Rom. 16:5, "also greet the church that is in their house. Greet Epaenetus, my beloved, who is the first convert to Christ from Asia."
- 1 Cor. 16:19, "The churches of Asia greet you. Aquila and Prisca greet you heartily in the Lord, with the church that is in their house."
- Col. 4:15, "Greet the brethren who are in Laodicea and also Nympha and the church that is in her house."
- Philemon 1:2, " and to Apphia our sister, and to Archippus our fellow soldier, and to the church in your house."
There are those who want to get back to the "Biblical model" of house churches by assuming that since the early Christians met in homes that is how we are supposed to do it today. But, the context of the early church meeting in house churches was out of necessity, not theological design. We are free to meet in homes, small buildings, or large ones. The important thing is that we don't become legalistic about it; and when Christians meet as a church, they should focus on the Word of God, honor God, and use their resources to further the Gospel of Jesus Christ.