Does gospel preaching matter? This is a question that Peter answers. Here are his words, from 1 Peter 4:17:

16 However, if you suffer as a Christian, do not be ashamed, but praise God that you bear that name. 17 For
it is time for judgment to begin with the family of God; and if it
begins with us, what will the outcome be for those who do not obey the
gospel of God? 18 And,

“If it is hard for the righteous to be saved, what will become of the ungodly and the sinner?”  19 So then, those who suffer according to God’s will should commit themselves to their faithful Creator and continue to do good.

What Peter says is this:

First, suffering is an indication that God may soon act in judgment.
Second, when God acts in judgment — and this need not be the Final Judgment but probably is — he will begin with the household of God (the church).
Third, from lesser to greater: if God is clearly just with the church then God will also be clearly just with those who do not obey the gospel.
Fourth, “gospel” is not defined but is assumed to have substantive content: and here we need to go back to the end of 1 Peter 1 where it dealt with the death and resurrection of Christ and redemption in Christ.
Fifth, the proper response to the gospel is to “obey” it. Why? It is a demand on us.