[spking]

I agree, many of these clichés are just verbal shortcuts to a pretty useful filter:

"This is not important for me to think about or discuss right now."

[FieIsay]

I think there's quite a meaningful difference between the suggested phrasing (which is quite honest and open, and I think should be generally acceptable) and the general character of the listed instances which serve to exemplify the concept, which dismiss the general (rather than contextual or personal, immediate) importance of the subject (e.g. "it's not that deep" rather than "I don't find it that deep" or "it's not particularly relevant right now"). I see it as a kind of refusal to take responsibility for refusal of engagement: external deflection of unimportance, rather than acceptance of non-engagement/disregard of (externally recognised) importance. I'd rather welcome people speaking as you exemplified: it's an explicit 'self-veto' from the relevance of the situation (and thus basis of involvement), rather than a dismissal of others' engagement (which ideally needn't involve the one who doesn't wish to be involved, of course).