Basically expressing my concurrence, though I think the full story is more complicated than that. Not just the house brands, but the manipulation of the secret ranking algorithms to put the most profitable (for Amazon) products at the top.
For example, why would Amazon care if some company sells you (via Amazon) a huge piece of shite as long as it produces the highest payback for Amazon? In the case of house brands there is actually some reputational risk if they cut the corners on quality too deeply, whereas they can let some other company do the same thing, temporarily boost Amazon's profits, and then Amazon just drops that company after Amazon has taken the profits...
Even better (or worse), Amazon will always claim to offer the best value. You were just too lazy to scroll down far enough to find it and too stupid to recognize it when you finally got to it.
But my bile against Amazon goes way back. My second and final Amazon purchase was decades ago. I didn't yet have the idea of "corporate cancer", but I could see what Amazon was doing with my personal data and it was clearly wrong. Nothing I've learned since then has improved my opinion of the company.