I think it is difficult to make generalisations. My very fit and alert father went into hospital at 92 with an infection where it was also discovered he had a failing aortic valve. The doctors immediately put his name forward for what was then an experimental new keyhole surgery technique for replacing the aortic valve. The operation was aimed at older people who may not survive open surgery.
The doctors reckoned that the operation would give him as much as 5 years more of active useful life. Unfortunately the infection was slow to clear by which time his heart condition was beyond repair.
But given how fit and busy he was, an active member of three local organisations, still driving, living independently, running his own life without any problem, to have such an operation at 92 seems not unreasonable. His chances of surviving it were high and he could expect to be in even better health after than before as his angina and breathlessness would have gone. He could continue to be a contributor to the welfare of his community for some years more and also be a contributor to the happiness of his family and friends.