I think laptops are very prone to failure. That is the cost of their compactness. The keys need to be thinner, the battery is expected to deteriorate over time, it will accumulate dust and will eventually heat up. If you want to try to give your old laptop a second life, you can probably bring it to a technician, have them clean the inside of the laptop, and let them do a fresh install of the system. It should be faster than before, but definitely not faster than what you have now. You can use it as a multimedia station or something.
Possibly, they pack a lot into a small space. IO had a MacbookAir for over five years though, and it only started failing towards the end of that time - unfortunately I replaced it with the Surface Laptop I mention here. lesson learned.
I'm thinking I'll take the laptop to a guy (or gal) and see if it can be addressed and for how much money; I know someone I could give it to who would appreciate it. We'll see. how it goes.