The heart is not necessarily the first organ to give out, the blood vessels themselves, non-dividing cells getting filled up with “junk” that won’t get cleaned

The heart is not necessarily the first organ to give out, the blood vessels themselves, non-dividing cells getting filled up with “junk” that won’t get cleaned up, all the space between cells do also to a degree. There never was evolutionary pressure to fix these issues (and there is none today either - people have children before 40, where these types of “faults” are not common yet).