I had a burner flip phone pay as you go for ages. It is 3G, lately I would text numerous providers and receive no answer. I would then use my 4G Lte and almost all of them would reply. I tried calling on my 3G and the screen would say dialing but your not hearing it dial as before.  I lived in small town market close to metro area and it seems to work fine there. I realized 3G is ancient, is this coincidence or do I need a new burner phone for hobbying.

It depends on your carrier, but some have been turning off their 3G towers. I would suspect this is issue in your case

Yes...it's time to upgrade your burner phone 4G or better.