I'm afraid that the moment you chose to use the word "wasteful" it became a philosophical discussion and they don't typically have final words at all.

The stripped down reason you see it as wasteful is that you have some set of beliefs about what is "right" and "meaningful" (many of which, I'll take liberty to say, most likely likely NOT consciously thought out) and since the core technical principle behind Bitcoin is simple enough, it's easy for you to see it does something that seemingly does not contribute to the fulfillment of what you consider "meaningful" (i.e. performing tons of computation that essentially compute nothing "meaningful").

Technical principles behind markets, industries or your own existence are not simple enough, so you cannot see through them and decide at a glance that they are "wasteful". And since you generally avoid falling into philosophical discussions (rightfully so), this is good enough for you. This doesn't mean that they achieve something that will turn out "obviously meaningful" to you (I'm cynical enough to assume they actually not), it's all just too complicated to tell at a glance.

If this is all too abstract, I'm saying that Bitcoin is actually doing something, and this something is much more complicated than the technical principle you can easily see behind it. You should take this into consideration when thinking about what this giant CO₂ emitting machine actually is. It is not a machine for computing hashes, as it might seem from a purely technical perspective.