It's rare (not unheard of, but rare) to work your way out of a PIP. In general, if you get put on a PIP, I would immediately start doing some soul-searching as to why I might be on the PIP and how I can improve AND I would start looking immediately for a new job.
Technically, there are two desirable outcomes to a PIP:
1) the employee improves and no longer needs to be on a PIP (rare)
2) the company successfully fires the employee and doesn't get sued because they covered their ass with a PIP
From HR's perspective (and the manager's), it is indeed the reluctant last resort, but it's essentially a win/win for the company. Either the employee improves, or they can fire them while minimizing legal risk.
In other words, it fulfills its intent quite nicely. It just doesn't always end positively for the employee. So I guess in that sense, it depends on which way you look at it.
The cure? Don't allow corporations to set your value, specially not mad and crazy corporations like amazon and space penis.
Because the rational choice is to take the high severance (being handed the PIP means your manager and manager's manager have already made up their minds against you, I've seen a coworker given an impossible task), that means that being an average Amazon engineer will have a 50% chance of being fired by your 5th year.
No matter how much you might try to "ace" it and put in your best effort, more than 9 out of 10 times, the person will not come out of it. Anything and everything no matter how minor is likely to be used as supporting evidence. So interpret it as a notice of eviction of sorts where they pay you some months to find a new job.
Yes, there are exceptions. Thing is do you want to try your luck with HR?
I feel it would have been possible to work my way out of it, I think different companies use them in different ways.
Ah well, most of the team got poached by Revolut anyway. I find WFH suits me a lot better because as long as I can go to stand up after a heavy weekend (which is a lot easier if you can do it from home) and then achieve above and beyond the rest of the week, there's a lot less anxiety.