Well you also forget that Theo is only part of the front office, Jed Hoyer is actually the GM. He's signed through 2021 as well.
What else could Theo do besides maybe take over an organization that has never won a World Series? I would guess he finishes out his contract and moves on to something besides baseball if he doesn't get extended by the Cubs again.
I think that with the right moves this current core of players can compete for a World Series but it would mean Theo and Jed finally moving on from guys they drafted or brought in which I think part of that is stubbornness on their part to admit it may just not happen for guys like Schwarber here and they missed their chance to cash in on him when his value was at it's peak a couple years ago. I'm sure they are afraid that if they traded someone like him then he'd finally hit his stride on another team and they'd feel like they didn't wait long enough but I think you are kind of at the point with this roster you can't waste your best years of Rizzo, Javy, Bryant, and Contreras hoping other guys will finally break out too.
The rotation isn't that young so it will be interesting to see how they fill Hamels spot but Lester is on the decline at 35, Darvish is 32, Quintana 30 and Hendricks 29. Hendricks and Darvish are both signed through 2023, Lester through 2021, and Q they likely will pick up his $10.5 mil option but he's a free agent after next year then so they basically will be looking to replace 1 starter each of the next 3 off seasons. They still have a year left of Chatwood too which I hope is not their solution to SP5 next year and I don't think Alzolay is ready to be a regular big league starter yet, especially with his injury problems.