He showed enough decent flashes last year to where I think the optimism is warranted. Plus you throw in Steichen and I think they have a nice setup. The Colts are closer to being even with the Texans than I think most fans would admit.
I don't think AR will fail outside of injury, depending on what you define as a failure. I think his skillset combined with the head coach will allow an offense that is good enough to be effective. To be great he'll need to develop as a passer.
My two concerns with him are (1) he seems to be fragile, which would partially negate his exceptional athletic ability and (2) he is VERY unproven as a passer. He did not impress me at UF throwing the ball despite the highlight reel plays.
He's lined up at FB and TE for the Rams in addition to WR. He's a special teams guy and team captain. End of the roster type. Might not make it out of training camp, you never know.
If you're an optimist like me, we'll hit on several of the lottery pick signings and emerge with unexpected stars which others deemed busts too early for various reasons. No matter what happens, I like Caserio's work. I'll bet right now we have more cut players get picked up by other teams within the first month of the season. This is figurative of course since my discretionary budget is $6 per week.
