Yes, modern surgery and modern rehab is much better than it was. However it is not instantaneous. I have heard from multiple orthopaedic surgeons and physiotherapists (via podcasts and articles) that there is a difference between healthy enough to return to the lineup, and the shoulder being at 100% of what it is pre injury. It can take 18-24 months post surgery for his shot to be back to the quickness of release, and power as he had prior to the injury. As for other players, yes they eventually got back to normal but often had a down season after the injury before coming back to 100%.
That said things are rarely, if ever, just one thing. I do think you are right in Dach's absence and the other injuries like Newhook, Pearson, RHP (until now) and others, plus the struggles of Anderson and Armia have meant there has been a lack of a second/third line scoring threat and more attention on the Suzuki/Caufield line. This is a factor too.
Meanwhile his defensive game and playmaking have both improved this season.
So I'm not really worried about Caufield. I think he'll be fine as the team improves.