(This applies far beyond acting. Why did a co-worker explain a concept this way, instead of that? It'll tell you something about their thought process - and yours - if you give it some attention and some thought.)
It will save a lot of internal frustration if I nail that!
Your description really meshes with my experience playing classical guitar. It takes a few months of work to memorize the piece, but then the fun begins. I've played the same piece hundreds of times. Instead of it getting boring, I keep noticing some new thing in the piece every week, it constantly feels "new." Bring out the bass for these two beats on this measure; hold this melody note just a tad longer; the harmony in these two measures makes for a great descending line, make sure the notes connect. Stuff you don't notice on your first couple dozen plays, that endless repetition starts to bring out. It doesn't work for every piece, but for my favorites, it's really a bottomless hole, like you said.
Like I say, I'm a numbskull when it comes to music, but I love live shows. I'm able to pick up those performance moments - the nuanced attention; the communication within the ensemble, and with the crowd - and just let the sound wash over me. I've had incredible experiences attending concerts by bands whose music I hate on recordings. The Dandy Warhols come to mind: I literally can't stand the one or two tracks I've heard by them (godawful noise), and I've no idea what "music people" think of them, but they were so in sync that seeing them live was transcendant.
That's an interesting perspective on performance for me as it parallels one of the aspects I enjoyed about performing stand-up comedy regularly for a time (primarily at open mics): getting to observe/analyse/theorize what contributed to whether a particular "bit" "worked" or not--both for myself and others.
For my own performances, I could choose a different word, phrasing, tempo etc and see how/if that affected audience response.
Equally, learning from observing the impact of when other performers did the same, refining their set over multiple weeks.
And, then, also seeing how other factors we had less control over (you know, such as the audience :) ) had an impact: sometimes same line, same delivery, might kill one week but got crickets the next.
Granted, my approach to comedy might lean a little more... analytical than some. :D
One of the best directors I worked with had the dictum that "you can coerce a laugh, but you can't coerce a gasp." Like, if you know some basic stagecraft you can make something funny, which... ho-hum. (On a related note: God I hate corpsing. 95% of the time it's fake, and represents to me a failure of craft.) But a wholly involuntary reaction? That's gold.
The best performers, in my experience, are craftspeople at heart. There's an analytical level you have to reach in order for the magic to happen in a reliably repeatable way.
That of course assumes that the script writer is infallible. Maybe you do understand the scene and the character deeply, and the writer screwed up by choosing the wrong synonym.
That's not to say there isn't bad writing, and bad shows. (God knows I've done a lot of both!) It's just that actors, at least for scripted material, are secondary creators. Our judgement, too, is not infallible - and we're in the worst position of all to judge.