Genuine question, why do most articles discussing PE seem to portray them in a malicious light? Fundamentally, PE investors have skin in the game - they do invest on behalf of their LP, but typically GPs contribute a portion of their own income into the fund as well, not to mention their compensation is tied to performance. The consequence of that gives them every incentive to help a company succeed, and not ruin it.
Sure there are failures as with every investments, but one can simply evaluate the overall returns within the asset class across a period of time to see that there is value being created (or at least allocated)
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.
Sure there are failures as with every investments, but one can simply evaluate the overall returns within the asset class across a period of time to see that there is value being created (or at least allocated)