1)Get a different phone or keep your old phone. Noone's forcing you to use one without a headphone jack. You could even use an older iPhone if innovation frightens you in general and you're happy with your old setup
2)Get/use an adapter. THey're not expensive and sometimes come with the phone
3)Get/use headphones with the new style of plug. You could probably use some new headphones as they get pretty janky over time
4)Use wireless. In lots of ways it's objectively better. Yeah you may need to get used to a new thing, but being good at adapting to change is an important muscle to exercise.
Honestly every time there's innovation there are all kinds of complaints, especially on here.
"Why do I have to change to USB-C? I'm fine with my old peripherals" (well your old computer still works with your old peripherals and if you want to use a new computer there are adapters).
"Why do I have to change to wireless headphones?" (you don't. Your old phone still works with old headphone jacks and there are adapters)
The idea that older people are completely unable to handle plugging a headphone adapter in but are somehow able to plug a headphone jack in is just bizarre. You can just pretend that the adapter is part of the cable with the headphones and always keep them together.