I don't think the Spencer Turnbulls of the world are bad, but I don't think the Cubs have much to offer someone like Turnbull, either. If you're Spencer Turnbull, you're likely looking for an MLB opportunity to rebuild your career. You're might not get a guarantee to start, but you'd like a pathway. The Cubs don't need to be giving Turnbull's a chance at this stage. We're past the "maybe if we can fix this guy, we can use this guy" stage, IMO. This is a team who, after missing out on Ohtani, will likely still need to win on the margins. Not desperately, but it's not going to be a juggernaut. We have multiple arms I'd far rather see start games. We have other arms who will be useful in the bullpen. It's time to leave the rebuild well in the past and make sure innings are going to arms you trust more.
In 2021, I'd say that the Cubs would be a decent bet to take a Turnbull, find something there, and flip him at the deadline as a useful bottom rotational arm for a contending team who was wracked with injuries. Maybe a Washington National type team does that for Turnbull and in July, the Cubs are wracked with injury and we'd like him then. But as of now, while I don't think he'd be an awful player to gamble on for a team, I just don't see the Cubs being able to offer him anything. He's the kind of guy who can probably offer some rebuilding team something, but as a contending team who's less than a juggernaut, probably is too much of a risk to give him much of a chance.