1. Someone has to physically assemble those Cisco routers. -Manufacturing/Production/Distribution Jobs
2. Someone has to design and test those Cisco routers. -R&D/Testing Jobs
3. Someone has to maintain those routers. -Customer Service/Support Jobs, as well as Firmware Updates.
4. Someone has to install those routers for customers -Setup Jobs.
I can go on-and-on-and-on for each of those examples of how one job closure opens a slew of fewer.
FTFY. The more efficient production does not open doors to more better jobs, it opens doors to fewer jobs--whatever the displaced can find. Those jobs may pay more, sometimes, but less people are going to be required to maintain the router-building machines than were required before, when humans were doing it all. Eventually the humans assembling modules that the machines actually made will be replaced, just as the people actually making all the parts were years ago, and the people maintaining the previous machines will just learn how to maintain the new ones in addition. Not only that, but machines don't even have to do the replacing. Chinese lives don't mean squat, so they can do just as well as human labor, to the same effect as machines (and, without even having all that domestic maintenance to pay for).
The R&D and service jobs are likely to stay, but the rest are just one economic innovation away from removing the number of available jobs, while the available workforce is not shrinking to match. Even the service jobs can get to needing less time per worker per issue, leading to fewer total service workers needed, over time. For example, there's no reason most of it could not be done remotely, removing the need for amny costly local service workers.
The doors don't open that way.
They just close. Opening them is an entirely different effort, and needs demand, and the ability to supply it. The magic thinking that greater efficiency opened doors is from a bygone era when potential production capacity and demand for goods were both inconceivably larger than what our entire workforce could manage (post-WWII into the 70s, at least, there was a constant shortage of domestic labor). Without a large and healthy industrial base, which we largely don't have anymore, new wealth is mostly being created elsewhere, by others, with jobs, and related spending, that we are only very lightly connected to, and which do not represent any new opportunities for us.
Short of an unlikely huge cultural shift in values, that's not likely to change any time soon, either. By and large, this has been coming down based on the short-term wants of several generations in succession. Deluding kids into thinking they will have opportunity if they just do what they're told, and buy what they're sold, doesn't help, either (but, hey, it pacifies them for ~20 years), nor do colleges being allowed to be disconnected from the job markets, while pretending to prepare students for jobs (though, is that any worse than a public babysitting institution pretending to prepare students for jobs or college, yet doing neither?).