There are two ways to think about this.
The first is that once your car gets too broken to repair, you should just ditch it and get a new one.
The other is that once your arm/ankle/hip/liver has problems, you should just transplant a new one instead of doing physical therapy/exercise/eating healthier/drinking less.
In my experience, marriage is much closer to the latter situation than the former.
If you're curious what those "fixes" are for the latter, see https://www.gottman.com/product/the-seven-principles-for-mak....