Translating a sentence with までだ

Question

Yesterday, I read a passage from Shin Kanzen Master N1:

As I was reviewing it today, I remembered that それまでだ is an expression which means "that's the end" or something to that effect. That said, I still don't understand what the last sentence of the first paragraph means.

I would translate it as "That is just in the movies and one is sitting while watching it, so it's inconsequential and that's it, but the audience forgets himself/herself." (I'd appreciate any correction to this translation.)

At this point of utter confusion (and desperation), I used Google Translate, DeepL, and other tools to translate 何のことはない、といえばそれまでだ。which led to equally confusing translations:

• DeepL: "To say it's nothing is an understatement." (it somehow makes sense but I don't know how it relates to this explanation)
• Google translate: "Until then, if nothing happens." (misses the idiomatic use of それまでだ)
• Yandex translate: "It is up to that to say that there is nothing." (???)

I would really appreciate any input you have on this. Thanks in advance!

Answer 1

I think you can consider ～といえばそれまでだ to be a specialized idiom derived from ～それまでだ. It carries a nuance that can be written like:

If you say —, you're not wrong and that's a way to end the discussion.
If you say that it's nothing more than —, I can't say anything.
It's true in a sense that it's nothing but —.

This is a common phrase as such.

それは別に映画の話であって、自分はいすに座ってそれを見ているのだから、何のことはない、と言えばそれまでだが、そんな観客としての自分のことは忘れてしまっているのだ。
Objectively speaking, it is true that you have nothing to worry because it is just a movie and you are only watching it from your seat, but you still forget about yourself as the viewer.