I think it depends. I've got family members who are in their late 80s, fit as a fiddle, living independently, taking care of their own finances, and enjoying their hobbies.
Notably, they also took good care of their health, stayed active, and didn't let themselves mummify after retirement (picked up new hobbies like woodworking and gardening). One family member of mine actually suffered a stroke and even their doctor was worried it would be the end for them given their age, but they cleaned up their diet took their health more seriously and really turned things around.
Make sure you've got plenty of muscle even into old age (as it helps prevent bone fractures and acts as a buffer when you get sick), don't eat like shit, keep a close eye on your health especially after middle age, and make sure you stay mentally and physically active. II don't know how many people I've seen simply waste away after retirement because they had nothing to keep them going after retiring. No hobbies, no friends, no interests. I think for some it really did just kill them from the inside out.