Isn't it super bad for the economy when you have a larger retired population than a working population?

The fact that Americans are starving is insufficient to prove your argument. There could be other factors contributing to this than a lack of food. Last time I checked, my grocery stores are still stocked, so I don't think they are starving because the stores near them simply lack food. My alternate hypothesis, is that this is a symptom of economic inequality and insufficient social safety nets, not a symptom of insufficient resources.

The same can be said for the argument regarding automation. Automation will certainly change our job system, but will it result in a severe net decline in jobs? That is an entirely different question, and research has shown that Automation may actually increase the size of the job market and the average wage of jobs.

https://www.sensrtrx.com/robot-automation-can-actually-create-more-jobs/

However, even if we have to cope with a post-scarcity economy, the solution to that isn't necessarily reducing the population. Automation generates economic product and increases productivity and efficiency of manufacturing, which maintains a source of highly taxable capital which can then be redistributed to the people. This will very much change our society and economy, however, it isn't an existential threat, by any means.

I can also go further and describe the negative consequences of a declining population, however, I see no point if you cannot prove the fundamental assertion upholding your argument.

This is very poorly reasoned.  No matter what, the number of jobs available will always be based on the size of the population.  More people equals more people buying stuff and needing services.  If we cut back the number of people in the country then jobs would naturally decline as well.  Job loss due to automation will happen regardless of population size.  Cutting immigration or curtailing population is not an answer.  Training and emphasizing job sectors that aren’t in danger of being lost to automation is the answer.

Guns aren’t all that expensive... if people want a gun here... they have one...

Don't worry corporations already have a plan for that.  Pay as little as possible thus ensuring that one has to work the rest of their life without retiring.

Chinese Comunist Party is in panic mode trying to increase China fertility rate, which fell bellow 2.1 in 1990. It means, accordind to the statistics, its pobulation will peak between 2025 and 2030, and will only shrink from now on.

It's bad because currently, the pension system is a Ponzy scheme where the working population funds the pensions of the retirees. If the working population shrinks while more people apply for retirement, it means either the shrinking working population will have to be taxed more or the retirees will suffer large cuts in their retirement benefits.

Well there are like billions of them so shrinking might be a good thing.

Gas station attendants only exist in NJ (and apparently Oregon) where state law requires attendant to pump gas.  There might be a few full service stations left here and there but for most part it is self pump.  Only time I saw one in real life is when I rolled up to station in my college town and got out to pump gas when a guy came out and was like these are full service pumps you gotta back up to self serve.  I looked at him dumbfounded because never been to one before and was like okay I'll back up because think they charged extra for service.

https://en.m.wikipedia.org/wiki/Filling_station_attendant

Haha, that’s just Oregon.  It is hilarious when you hear somebody in Oregon justifying it too.  People that have lived in Oregon their whole lives are scared to death of gassing up their car themselves.  

Also, it is super annoying every time I drive through Oregon and have to park next to the pump and wait for a dude to lift a nozzle and put it in my car for me.  Dumbest law ever.