I mulled over this question today, while mowing the grass.
The backpacking community has the benefit of tremendous advances in so many aspects of hiking - lighter gear like packs and sleeping bags, better clothing, better and lighter shoes, better nutrition, better hydration, better support systems (phones, shuttles, hostels), better ways to ward off ticks and insects, electronic access to up-to-the-minute info on weather, water, camping spots, etc.
And yet, so far as I know, the percentage of backpackers completing a thru hike is about the same - roughly 25%.
Why is that?
My first guess is that all those advancements are, even cumulatively, small things in comparison to the enormity of backpacking nearly 2,200 miles. Physical effort is 99% of undertaking, so we are maximizing the remaining 1%.
It is also possible that the advancements have been offset by certain detriments. We are less physically active than past generations, so need more "help" to bring us up to a level of comfort and capability that matches previous generations.
Whether we are using trekking poles or not, carry a smartphone or not, treat our clothes with permethrin or not, use electrolytes or not, prefer running shoes to boots, and any of three dozen other things, is just small stuff. In the end, we still are toting heavy packs up and down big mountains for 2,000 miles.