nom – while I do NOT disagree with you, I do have to disagree about it not being a comforting thought to the mourners. I found it very comforting to think of the cosmic implications, spiritual value etc. But I still don’t think that it is something you should say to me during shiva. During shiva we want to be validated in our pain, and if you want to tell me why I should not be in pain, I don’t want to hear that. But to tell me that this loss is horrific for me, but possibly helpful for the good of klal yisroel, well that was very comforting. For me. There is just a time and place for it and I think shiva is about acknowledging the suffering of the loss.
You added “avoids what the life of the departed was like – and even more – could have been” It never occurs to me that there was a could have been. If Hashem took my sister at 17, there was no 18. there was no 19. I don’t think He invented a scenario of a future and then changed His mind.
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I MUST add that these are MY personal thoughts – oddly enough on this day of that sister’s 37th yahrtzeit. No two mourners are the same and all those people who write letters and books on what to say and what not to say to mourners are doing a disservice. I found some writings telling people not to say those very things that I would have loved to hear. Having sat shiva 3 times in 6 years does not make me an expert, ch”v, but I have learned that nobody should be so bold as to denounce someone for their comments without being absolutely sure that there isn’t a mourner who disagrees.