Here's another perspective - I've seen PE firms do as you described, cut costs and fire employees, just as much as I've seen them inject more capital into a business and help them with further M&A. Having better user experience can lead to increased revenue (better product, improved branding - leading to increased market share for example) - which should equally be an incentive to PE firms as well.
None of the anecdotes you mention counteract the nature of the industry as whole: https://caia.org/blog/2022/07/20/long-term-private-equity-pe...
I've already caveated that bad investments may occur. My question is why the negatives are being focused versus the positives?