You say “Capitalism — left to its own devices — bends towards inequality.”
If would be more accurate to say life “bends towards inequality.”
Freedom requires equality of opportunity, not equality of outcome. People are born with different abilities and disabilities: it is inevitable that some will do better that others, because of the different cards they were dealt, or because of the intelligence and effort they put into playing the cards they were dealt.
All people are given the right to the pursuit of happiness, but no-one is guaranteed to attain it.
Your solution appears to be redistribution of wealth earned by others to the less fortunate, and increases to the minimum wage. You point out that Seattle has both a $15 minimum wage and low unemployment and falsely conclude that raising the minimum wage will not increase unemployment. The correct understanding is that social inequality can be addressed by “redistribution of wealth and increases to the minimum wage” as long as these interventions in the free market are not significant enough to break the laws of supply and demand. Try a minimum wage of $40 per hour, and see what happens. Try an unemployment benefit of $50,000 per annum, and see who bothers to look for work.
Government’s role is to ensure that Companies and employers behave ethically within the Capitalist market, and to provide survival assistance as a safety net for those who are unable to support themselves, not to attack the free market itself. Capitalism has been around as long as the concept of private ownership of property, probably since humans lived in caves, and capitalism is just economic reality; the nature of the free market. Only a fool would deny that Capitalism is the greatest engine for wealth generation ever seen on this planet. The fake economic theory based on equality of outcome for the sake of mythical “fairness” is called Socialism. It has been tried all around the World for over 100 years, and no-one has ever been able to make it work. Central Planning just does not work: it eliminates the price signals that adjust supply to meet demand in the Capitalist free market, replacing them with dictates from bureaucrats, which results in surpluses of things no-one wants, and shortages of things people do want. People end up with equality of outcome: as the economy fails, they are all equally as poor as the poorest of today’s homeless people!
In answer to your question, we excuse the “excesses of Capitalism” because Capitalism works: no other system does.
For a solution to homelessness read https://medium.com/@abs4fr/which-side-of-history-would-you-like-to-be-on-74e2aac90c16