I sympathize with your views in that a formalisation of meaning in life would seem to take away from it somewhat. However, your response also comes across as putting a stake in the ground and thereby closing your mind as to what the utility framework has to offer.
These are some of the problems with utility I took away from your comment:
1. Short term utility maximisation does not necessarily align with long term utility maximisation.
2. The utility is difficult to define because we don't know what can contribute to it and how much those components would contribute.
3. The utility, even if defined, can only be partially observed.
While these are certainly valid and interesting observations, that doesn't mean there isn't a latent utility that describes your lifetime's value. If you live a thousand lives and had access to a device to measure the (latent) utility, surely you could it to rank lives as more meaningful or valuable than others.
Looking at it this way, the problems you raise could be seen as opportunities: how should we align short term utility with long term utility? How can we find out which utility components there are and how much they would contribute? And how can we make the utility observable, so that it can be maximised?
Interestingly, attempting to maximise the utility may itself lower the utility as a result of spending time on the maximisation task and the dehumanisation of life as a result of its formalisation.