Jacob does not shame his firstborn without also showing him a door. Targum Pseudo-Jonathan opens Genesis 49:4 with a startling image: "I will liken thee to a little garden in the midst of which there enter torrents swift and strong, which it cannot bear, but is overwhelmed."
Reuben was not evil. He was a garden. The soil was good. The problem was a flood of passion that rushed through faster than the garden could hold. The Targum names the sin plainly — the incident with Bilhah, his father's concubine — but it does not define Reuben by it. It calls the sin a torrent, something that came through him, not something he is.
Then comes the line that made Reuben a patron saint of teshuvah in later Jewish tradition. "Be repentant then, Reuben my son, for thou hast sinned, and add not; that wherein thou hast sinned it may be forgiven thee." The Aramaic presents repentance as an invitation, not a verdict. The sages later teach that Reuben was the first person in the Hebrew Bible to perform complete teshuvah (Bereshit Rabbah 84:19), and this Targum is part of that reputation. The garden was overwhelmed. The garden was not destroyed.