Yes, because that new SUV will probably remain on the market for another 20 years. The 1999 Opel Corsa has at most 5 years of useful life left. So "new SUV" vs "old car" is a false dichotomy, and the real comparison should be between "20 years of fuel-guzzling SUV" or "20 years of fuel-efficient minicar" (mildly exaggerating, but you get the point).
So destroy anything that could be useful and reliable (which in turn decreases emissions as well because less things are being produced) and buy new shiny cars? Have you ever looked at how reliable modern cars are (especially with downsized engines which don’t do much about fuel economy but do a lot in reliability, not in a good way? you can’t expect most of them to last 20 years on the first engine and gearbox. While over 300k miles on the odometer was totally doable with 20 year old cars which are often rust free(not like 70s cars) and similarly efficient as modern cars, I don’t see why buying a new, more unreliable with almost the same fuel efficiency car would be better for emissions than keeping an old car running.