Anyways... I have posted a few comments already, but here is my two cents:
Treliving is not the worst option out there. His record in Calgary seems to be best characterized as "mixed," which is to say that there is some good, but there is also some bad:
Trades
Both Hamilton trades were really good (acquiring him for a mid-1st and then returning both Lindholm and Hanifin a few years later) as was the Toffoli deal with Montreal (late 1st plus B-prospect) and, while the Tkachuk trade turned out bad, the return was solid for a player who wanted out (#1C, top-4D, 1st rounder).
On the other hand, he's had some stinkers. Sam Bennett for a 2nd rounder seemed alright at the time, but amounts to very little when you look at how Bennett has blossomed in Florida. The 12th overall pick (used to select Noah Dobson) and two 2nds for Travis Hamonic is also pretty rough in hindsight as is trading a 2nd (used to select Jordan Kyrou) and 3rd for one year of below average goaltending from Brian Elliott. For some reason, Treliving also decided to acquire Nick Ritchie last year.
Drafting
I am not familiar with Calgary's prospect pool and don't feel like spending the time to get familiarized, but it isn't rated highly. That is somewhat concerning given that the Flames have not exactly been a contending team over Treliving's near-decade at the helm: they had only two seasons with more than 100 points.
On the other hand, he has found some nice players outside the 1st round who are now contributing at the NHL level: Rasmus Andersson, Andrew Mangiapane, Adam Fox, and Dillon Dube. He is going to have a bigger budget and scouting team in Toronto. Here is hoping he can use those extra resources smartly.
Free Agents and Contracts
This is my biggest concern with Treliving. Huberdeau was given a $10.5M contract before even putting on a Flames sweater, Kadri is signed to a $7M deal until he's 38, and even a guy like Coleman is making $4.9M until he's 35, well beyond the years that guys like him start to decline (see: Simmonds, Wayne).
Beyond the current roster, Treliving also has a claim to some worst deals signed in the last decade: Troy Brouwer was given a $4M/4y despite being 31yo when signed and having a career high of only 43 points, and James Neal was given $5.75M/5y despite also being 31 and in clear decline.
One of the best things that Dubas did was avoid giving big money to a middling player on the back end of his career. If Treliving hasn't learned his lesson, then it is only a matter of time before we end up with another Clarkson situation.
Overall
Treliving has been GM of the Flames for nine years: He's missed the playoffs in four of them. If he had some sort of magic formula to build a winner, he certainly hasn't shown it. At the same time, there are positives in his record, in particular his trades (something that may be particularly relevant for us). I see no reason to be optimistic about him, but I also don't think his hiring portends impending disaster. He's not Peter Chiarelli or Marc Bergevin.
Is "meh" good enough? Maybe. We have seen more than a few objectively bad teams go on hot streaks at just the right time and end up in the Conference and Cup Finals. Perhaps we see that happen with this much more talented group. On the other hand, Shanahan put this franchise in a difficult spot: We once chased the biggest names in the business. Now we have been forced to rapidly hire from a mediocre cast of whoever is available. That plainly sucks.