Many of the original Star Trek episodes look like a TV play too. Lots of backgrounds that are just colored lights where today you'd expect to see some setpiece. It's all about the story anyway.

Soviet TV play adaptation of Asimov's "The Naked Sun". Has the best looking robots. (See the beginning of part 3 for example)

https://www.youtube.com/watch?v=fQWLsZurF5U

https://www.youtube.com/watch?v=2YksNxkF2TQ

https://www.youtube.com/watch?v=BPamQ-khmf8

TV plays also used to be very common in the UK.

The best adaptations of Shakespeare were TV plays. A lot of CGI is now trying to mask the lack of good plot.

I also think many classic TV shows are effectively TV plays - such as Star Trek, the Twilight Zone, etc.

You're right, that's a really fascinating observation. I can see myself noticing that on future shows.

You mean something like UK's "I, Claudius"?

Which, once you get over the low production values, is actually a very good series. Amazing actors, including Derek Jacobi. I once saw Derek Jacobi and Robert Lindsey in a play on stage, Becket, which had a few cloths and spotlights as props. These people can act. It was amazing.

I never considered it a bad series. We had it on TV even behind the Iron Curtain before 1989.

From what I've seen on youtube regarding British TV plays, they were much much higher budget, and much closer to just a normal TV series/film, maybe with a theatrical dramatic flare, while Soviet TV plays often had abstract "modern theatre" like decorations, fewer or no background characters, other cost cutting measures, much closer to theater in terms of production.

The production values of this Soviet Lord of the Rings strike me as quite similar to I, Claudius. And it's worth noting that the televised low-budget stage play production values of I, Claudius notwithstanding, it's one of the best television shows ever made.