I'd say it's somewhat the reverse: Amazon was vastly better for things they sourced and sold themselves. I couldn't get everything there, but things they did have, I could trust.
They tried to expand into absolutely everything, and that's what feels like broke even my trust in the stuff they sell directly (since they also have comingling of third party inventory on that stuff, now).
I'm saying that no, that's silly. They're less dominant because they're seeing significant competition, and the stuff you perceive as "worse" is the inevitable result of them having to squeeze on margins or expand into higher-hanging-fruit regions of the market.
And we're all richer for it. Don't buy from Amazon, that's fine. But don't expect to live in a world where you get someone else who can dominate a market like they did, either.
That's literally the definition of a lack of competition. Everyone loved Amazon because they were cheaper and faster and better. Even inside the tech microcosm, no one makes a purchasing decision based on "love".
That's probably true, but the truth is that situation was an unstable equilibrium in the first place. There's absolutely no reason in a functioning market to expect (or want!) one provider to be the uniform best option at all things. Eventually everyone else starts competing.
To wit: the situation over the past decade wasn't so much defined by Amazon being better (or "not evil", given the framing I'm saying here), it was that everyone else sucked. Now they don't suck so much, and Amazon is having to compete in ways (like profit!) they used to be able to ignore.
That's a good thing, not a bad thing.