It's not that support doesn't make a market difference, it's that customer loyalty is a liquidatable asset, and almost everyone wants to retire someday, so good companies almost inevitably will eventually become bad companies and cash out all the good will they've accrued over years and decades.

The only possible solution is some sort of regulation of transparency in ownership structured similarly to banking regulations (routinely moving amounts of money just under reporting limits or in any other way seeming to attempt to dodge scrutiny is considered malfeasance), so customers are promptly and continuously informed when Mom and Pop Shop is bought out by Established PE Vultures™ or Scrappy Small Business gets acquired by S&P #342, Enshitiffication Incorporated or a majority of Public Infrastructure Corporation is owned by Slacktivist Investors Group.

I want it to be obvious, and I want ownership to necessarily be as prominent as branding. "A Unilever Brand since 2003" needs to be just as big as "Natural Small Local Foods Coop Inc, since 1913," so that we can start to associate the corrosion of service and product quality with ownership and acquisition and corporate mandates, and any attempts to overly convolute the source of a clear business direction with scattered minority ownership just happening to band together needs to be treated as fraud.