In This Day And Age Of Moral Uncertainty, Shouldn't There Be A Heavier Focus On 'Thou Shalt Nots & Thous Shalls' In Sermons And Teachings?

In this day and age of moral uncertainty, shouldn't there be a heavy focus on 'thou shalt nots & thous shalls' in sermons and teachings?

The answer to this question depends on the desired outcome or motive. 
Yes, the church should focus more on ‘thou shalt nots and thou shalls’ in order that the church might learn God’s Will and understand the difference between righteousness and sin.  Discernment is a great need for the church in this present age.  Furthermore, in studying God’s perfect will the actions of the church are put into contrast to God’s perfection and as a result sin is revealed and brought to light.  As a result, this drives the church to contrition (i.e. repentance) and its continual need for Christ’s forgiveness and grace.  This is good!
On the other hand...
No, the church should not focus more on ‘thou shalt nots and thou shalls’ in order that believers may ‘acquire’ and be ‘motivated’ to live a victorious Christian life.  The reason being, the Law does not properly motivate or make a believer more holy in thought, word and deed.  The Law reveals righteousness but does not grant or as the Reformers would say ‘impute’ righteousness.  Rather, that is the work of the Holy Spirit through the Word & Sacraments (see Q&A 208 in the Explanation to Luther’s Small Catechism).  Furthermore, Tim Ysteboe in the book We Believe states, “Sometimes people believe that they are saved by grace, but that they remain saved and grow in sanctification by works.  Paul’s epistle to the Galatians is an essay to the contrary.” 
Trying to live out a fruitful Christian life by the motivation of ‘thou shalt nots and thou shalls’ rather than the Holy Spirit through the Word & Sacraments will ultimately lead to one of two polar opposite results: self-righteousness or despair.  One living by ‘thou shalt nots and thou shalls’ goes the way of self-righteousness when they deceive themselves into believing that they can actually accomplish the demands of God by their own strength and abilities.  On the other side of the coin, one goes the way of despair and hopelessness when they look at the ‘thou shalt nots and thou shalls’ and realize the enormity of its demands.  Either way, self-righteousness and despair lead us away from the accomplished work of Jesus on His Cross for us.