I've described the four missions of the Church as process oriented, not goal oriented. This is not criticism. Process or systems thinking is the best way to achieve improvement. A system consists of things you do every day that lead to better outcomes, such as studying the scriptures and praying.
Let's say you set a goal of reading the Book of Mormon in 3 months. This is not really a goal; having read the Book of Mormon in 3 months is not the point. Instead, this "goal" is really the establishment of a system that will lead to better results, even if you don't know ahead of time what those results will be.
In like manner, the four missions of the Church set up systems that will lead to better results.
The reason I advocate a "Fifth Mission" that is goal-oriented is because a system without focus or purpose can become rote and even meaningless. It risks becoming a set of rules and performances that people come to resent.
Think of the law of Moses. It was intended to lead people to look to the Messiah, but it became too much system and not enough goal. People began to think the performing of the ceremonies and observance of the rules was the point. Consequently, they didn't recognize the Messiah when He came.
I think there's a risk of a similar thing happening with the four missions of the Church. We're not preaching the Gospel to get baptisms or to persuade people to choose our church or religion over another one; we're preaching the Gospel to give people an opportunity to come to Christ and help build up Zion.
Lots more to say about this, but I wanted to clarify the point that process-oriented missions are very important and more effective than goal-oriented missions, but process-oriented missions still need an ultimate objective.
Hence, the Fifth Mission.