There are so many texts in the Bible alone that refute the "easy-believism" that affects so much of modern Evangelical Protestantism. To be fair, there are many more faithful Protestants who have a view of repentance that is closer to the biblical texts, some of whom I know personally, but much of the Evangelicalism one encounters is that one that has a very weak, if non-existent, view of repentance. What is ironic is that these same people who lambast Latter-day Saints for rejecting Sola Scriptura hold to a theology that is antithetical to the Bible, something one finds when one critically examines many of the major doctrines of Protestantism (e.g., creedal Trinitarianism; rejection of baptism being salvific; the nature of justification; eternal security, etc.).
In Num 5:7, we read the following:
He shall confess his sin that he has committed. And he shall make full restitution for his wrong, adding a fifth to it and giving it to him to whom he did the wrong. (ESV)
In this verse, Yahweh Himself commands that a person to (1) repentant and (2) to make full restitution and (3) to add 20% extra to the amount he stole (cf. v.6), showing that repentance is not a superficial "I'm sorry," let alone being non-existent; repentance is, as LDS theology holds, a process in many instances such as it is spelt out here.