What timeline do the Raptors currently have? I don't see any way for them to get near contention without doing at least two major trades. And Lillard could be the first of the trades. Right now they are too good to tank but also more than just one realistic trade from contention away.
Having Lillard sets them up for a much better situation. Yes, the last two years on Lillard's contract aren't ideal. Paying 60 million for a 35, 36-year-old Lillard might be hard to swallow if he falls off. But I would argue hoping to pair a second star with Lillard in the next 1-2 seasons to become a contender is more realistic than hoping for Barnes turning into a superstar that can lead the Raptors to another ring.
It's not a no-brainer or steal for the Raptors but it also isn't messing up their near future. Because again, they have no timeline to mess up.