Thing is that we can still rewatch serious episodes like “Balance of Terror” without being distracted by limitations of that period. If you’re treating the story and the acting very seriously, the scenery kinda falls into the background, or you just handwave it knowing that the Star Trek universe developed differently from ours (faster in some areas than in others).
I happen to think "Balance of Terror" is a great episode. I judge what I'm watching in the context of when it was made and by whether or not they made the best episode or movie they could with the resources they had available at the time. And "Balance of Terror", just like several other episodes, delivered.
If "The Vulcan Hello" settled for only looking like TOS, then I'd know that they did
not put together the best product they could've with the resources available to the current production team.
I do know that DSC S1 would’ve worked better as a story if the year was 2456, the villains were the Qlang, and if Burnham had been adopted by Selek and T’Rell and raised on a Vulcan colony in deep space (or better yet, by a family from a brand-new Federation member). But they really, really needed that Vulcan salute poster (“Star Trek without LLAP? Gimme a break!”)
I'm going to refrain from wondering how about how DSC could've worked in the 25th Century until I've seen
Picard. A hostile Klingon Empire where the concept of peace with them is totally foreign and a Terran Empire in its savage prime are both things more conductive to a 23rd Century setting. Had
Planet of the Titans been made, the Crossfield Class Starship also would've been a 23rd Century design, as far back as the '70s.
A series set post-2387 and in the wake of Romulus' destruction is what I thought we'd get when a sixth Star Trek series was first announced in November 2015. Even though I didn't think we'd ever see Picard again,
Picard is actually more along the lines of what I initially thought we'd see. At least as a setting. That wasn't the story they wanted to tell with DSC, so I don't have an issue with them setting it when they did. In fact, it probably worked out for the better, because
Picard doesn't have to worry about what another series did when it tackles post-
Nemesis, post-Hobus head on.