I think I haven't enjoyed Disco this much since season 2. This was a great episode in the tradition of whacky time travel episodes. And I really liked seeing the old uniforms, set designs, and Discovery exterior. Mainly because I like those designs much more than the 32nd century upgrades. The sort-of tie-in to the "Calypso" Short Trek also worked really well. And Linus was great as usual.
I was not a big fan until season 4 which I loved for it's slower pacing and overall themes, but I'm enjoying this one a lot for totally different reasons, like the ones you mentioned. Disco's cast really lends itself to "fun", on the rare times it attempts it.