These are valid concerns and I wouldn’t really argue against them. I at least partially share your scepticism about meaningful longterm impacts, after all. (Though if anything, then preventing our extinction in the next centuries seems like the most promising candidate for longterm change—but of course it is also questionable wether we can actually predictably decrease the X-risk probability within this timeframe, let alone on a larger scale.)
I guess I am just very pessimistic about our ability (and willingness) to do something meaningful about wild animal welfare (especially for insects) within the next few (hundred) years. Aside of in- or decreasing their numbers, which is not a consideration, as long as we don’t even know (with some certainty) if their lifes are net-positive or net-negative. So it seems to me as if the only possibility for a substantial change with a predictable outcome in the area of wild animal suffering/welfare might happen only if we survive at least a few hundred more years and have 1. the time to investigate the most crucial questions and 2. a shift within political/ethical considerations which would allow to implement larger-scale programs solely for the purposes of wild animal welfare. I have no idea if the second condition will ever be met, though...
Nevertheless, given the massive uncertainty about the solvabilty of wild animal suffering and X-risk prevention, I still think that the fight for farmed animals (especially the more overlooked ones like fish and shrimps) might actually be one or maybe even the top priority right now. At least it might be the most impactful action where we actually know that we have a positive impact at all… (And who knows, maybe if we finally abolish factory farming some day, our view on animals might also change and make the second condition more likely—but I’m just speculating at this point, so I’ll leave it at that.)
What are your thoughts on pursuing a PhD compared to 3-4 more years of work experience? How much career capital is a formal PhD degree actually worth?
This answer might depend a lot on the context, so:
I have a degree in pure mathematics and that is also where I would potentially pursue a PhD. I have high grades, but not from a top university.
I am living in Germany and am willing, but not eager, to move to another country in order to maximise my impact.
I am considering Earning to Give as my most impactful option (though I am far from certain yet). If I do not pursue a PhD, my next step would most likely be trying to asses my fit for quantitative trading: https://80000hours.org/career-reviews/quantitative-trading/ (To make matters more complicated, it is mentioned that you can enter the field with graduate degrees, but some roles do require a PhD. So if you are knowledgeable in this area, some advice would be especially welcome.)
I have neither a concrete plan nor a scholarship for my potential PhD (yet) and would change my university anyways. So it might also be a consideration to try some jobs and internships and pursue a PhD later on if worthwhile. However I am under the impression that returning into academia is more difficult than staying there.