Andersson is basically Willander's ceiling, and is signed for $4.4 million next year. And he's only 28 years old.
Unless the Canucks think Willander is ready to basically be a top four defensemen at the end of this year, and assuming the Canucks can afford to re-sign Andersson at the end of next season, then they should absolutely be looking at making that trade.
To me, it really depends on management's current projection for Willander. Because, if they think he can step in this season and play meaningful minutes, and then play top four minutes next season with room to grow, then ya, trading him for Andersson right now doesn't make much sense.
But if they think he is going to develop much slower, and won't, for example, be a top four defensemen until 2027-28, then they should definitely consider trading him for a player like Andersson.