That sentence doesn't mean that public opinion doesn't have weight.

It means that public opinion is complicated because people can hold more than one idea in their head at once.

Did it ever? That it has sounds mostly like a lie told to the public to placate it.

It's sort of the "why it works on paper" for capitalism. Nominally, it plus low barriers to entry/conversion plus anti-anticompetitive mechanisms/trust-busting/etc lead to power structure wherein only businesses which keep their customers happy thrive.

In practice, network effects/'brand name' recognition/QA make for a generally reliable customer base from those who don't remain informed or care about your policies/practices or are just used to your product, and that's even before high barriers to entry and other market factors limiting competition to those who engage in the same cost-cutting-oriented models and so end up optimizing the same way.

TL;DR: Probably not.