As mentioned in other reviews, this was not intended to wrap up the series. James Arness said in many interviews that the cast fully expected to be renewed given their season long ratings. But, the rural purge was underway and Gunsmoke was part of that now infamous programming decision.
That said, this is a whimsical episode, and there's nothing at all wrong with those, and this one was consistently funny. It's also nice that this season-ending episode featured Ken Curtis, who by this time was getting acting opportunities on par with James Arness. This shows how good an actor Curtis was, but also shows what a class person Arness was, in that he freely shared the stage with the ensemble cast.
In many ways, the kind of wrap this episode would have been, had the cast known ahead of time it was the end, would have been like the made-for-TV movie "Gunsmoke: Return to Dodge."
Sadly, by this time, Curtis rightly considered himself an A-list TV actor and wanted equivalent money as a star. The producers wanted to pay him like a co-star. That's why this episode ended up being the final performance Curtis had as Festus Haggins.
The ability to seamlessly combine comedy with drama is difficult, and in this episode, Curtis pulls it off very well. But, the entire guest star cast pulls off "lazy and manipulative scumbags" very well indeed! And that's what this episode needed.
Gunsmoke could have gone for at least another season with solid ratings. CBS owed the cast and crew the room and chance to craft a special send-off episode. The negative feedback CBS earned for this oversight is a major reason why successful series afterward were nearly always given that send off coda.