Doesn't the qoute state that income inequality is supposed to enact accumulation and growth("give something to aspire to") but instead leads to concentration of political power among the wealthy, who then use that power to further secure their higher income, creating a feedback loop?

That directly implies that removing income inequality and adding feedback loops that avoids excessive capital concentration is the way to go.

And to your point about non-coerced transactions, where does coercion start? Monopolies? Excessive costs? Does Comcast coerce their customers, if they have only no internet as the alternative? Does uber coerce people with surge pricing? And that pharma guy, raising the price of the drug, did he coerce people ? I would tend to say yes in the case of the Comcast monopoly, no in the other cases.

But it's hard to define exactly where coercion starts.

A more fundamental examples, from my libertarian socialist perspective: advertising in public view. Is that coercion of a third party(the advertised to?) Microsoft windows/ apple and other walled gardens with no data export, but payed for upgrade path and end of support?

And even more fundamentally, sometimes any and all transactions you make can be under duress and make you inherently dependent on the partner: Getting a shitty job that barely feeds you, because your skills are obsolete and your country doesn't provide basic income?

Startint that shitty job early, due to not having the same resources, stability and growing opportunities because your father is working a shitty job just to make ends meet?