I think what’s so hard about Tznius is that for the most part clothing depends on the person wearing it so you can’t just say this or that is untznius across the board since on one person it could be that it’s really not appropriate but on someone else its totally fine.
Also, when people start talking about tznius and the “extras” they tune out and it’s like well thats what you do but I do different. Since not everything is clear-cut, we all know elbows, knees, and collarbone and it shouldn’t be too tight. But the spirit of the law should also be followed. I heard this mashal from someone:
So these people just get married. After the Sheva Brachos the husband comes home one day and takes out a piece of paper with a list of how to be a good husband. Starts with, say hi how are you, honey. So he reads off the paper to her and goes through it. The wife will not be happy.
Same here, we could read off the list Hashem gave with tznius and check off what we do but that doesn’t mean it’ll make Hashem that happy.