I have many "progressive", "pro-eco" friends who just can't understand I am still using that old crappy Nexus 5X although I could afford a new, fancier phone (and my cell phone operator would subsidize it partly and nice person from call center would add another 4 GB of free internet to existing 15, as if I could ever use so much using cell phone).
They also cannot understand that I am still driving my 10 years old car instead of leasing/buying a new car which would be more "eco friendly". I am trying to explain them that cars are not growing on trees and producing a new one is not really that environment friendly and that during past 10 years cars were not improved so much in terms of CO2 emission to justify the change (giving recent car makers test scandals it is hard to say if they improved at all. Even if I could buy electric car, which is not really an option in my country due to lack of infrastructure and my usecase - I don't drive in the city, only long travels - still producing a new car emits more CO2 than my car will emit during its remaining lifetime).
Same with driving to work (they buy those new cars for a reason, not to sit in a tram among those sweating people), same with using electric laundry dries (it is so unfashionable to air-dry laundry at home), etc.
People love to talk about being pro-eco and taking actions that make them feel good, but they can't face the truth that their consumption habits change would be infinitely more beneficial.
If anyone else is wondering, I think you're right about this. I've looked into it and there are a few people who've tried to tackle the question of what's better but I find they all have some problem with the assumptions they make, largely because it's just a difficult problem with a lot of variables. Mileage, age of each vehicle, expected life of each vehicle, what emissions can be attributed to production, whether to include emissions of the inefficiencies of recycling one but not the other, etc.
I decided that a new eco-friendly car and a similar old used car were close enough in emissions - i.e. within the same magnitude - that it wasn't worth it if it's your only reason for spending the money on a new car. What's far more effective is reducing mileage done in a car.