One reason: the hardware has "improved" in ways that are not directly helpful for software. Executing CPU instructions more quickly doesn't help if you can't i

One reason: the hardware has "improved" in ways that are not directly helpful for software. Executing CPU instructions more quickly doesn't help if you can't improve memory speed. Having more cores doesn't help if you can't utilize them efficiently in your problem. But I agree with the meat of your point: modern software sucks and is getting worse.