> It becomes a charged subject matter when one works at companies like Google and Facebook and gets used to navigating performance reviews.
The way things were at Amazon when I was there, posts like this would count against a Principal Engineer promotion.
One of the standards engineers are expected to meet is "Respect what has gone before". You don't know the full details of what was going on at the time, you don't know the trade-offs and why, you don't know what they did and didn't know about the situation and what couldn't have been foreseen at the time decisions were made.
Generally speaking people aren't idiots. They do the best they can with what they have, under the circumstances they're operating within, to meet the goals they have.
Almost no one sets out to make a monster impossible to maintain, or with diabolical performance.
Treat it with respect, even while you work to replace it.