There is no point in buying a newer phone, iPhone or otherwise, unless the capacity is bigger. iPhones come in various capacities, and in general, the higher the internal phone capacity, the higher the price, hence the second part of any iPhones description, 16GB, 32GB, 64GB, 128GB, 256GB, etc. Only you can decide what capacity is appropriate for your needs.
Do you need to carry all your photos around with you all the time? Have you looked at devices like these for example, they let you offload photos, videos to a portable device local to you, freeing up phone space :- https://www.amazon.co.uk/s?k=iphone+usb+flash+drive&crid=17DAU0EUYFVMR&sprefix=iphone+usb+cable%2Caps%2C132&ref=nb_sb_ss_i_4_10