For those that do not remember, here are the episodes Chibnall wrote before becoming showrunner.
42: A "24 in space" episode that was kind of boring. I don't remember much about it.
The Hungry Earth & Cold Blood: The two-part return of the Silurians. It was not a good return, boring too (thankfully we would get Madame Vastra, a much better Silurian).
Dinosaurs in a Spaceship: As the title says. It should have been a cool idea, but it was mostly wasted.
The Power of Three: An interesting slice of life episode in the Pond household. This was so close to being great, but the ending ruined it. i just remember coming away annoyed.
Chibnall also wrote several episodes of Torchwood, including the much-maligned Cyberwoman.
So yeah, people had a reason to be concerned when he was announced to be running things. Glad he's gone.