Most of the time it isn't bad UI but a vocal minority that just hates any change.
It's not like these companies release these changes without doing significant user testing and AB testing. If you design based on the opinions of HN/Twitter, every site would look like Craigslist (or HN's favorite abomination of a design, the Berkshire Hathaway site).
Your justification for bad redesigns is that... other companies do it too? That's a very apathetic/defeatist attitude.