The Centralization Issue and Cryptocurrency

I've seen lots of talk around "centralization" occurring by putting too much power in the hands of the miners. However, mining itself is a completely decentralized activity - is it not?? Anyone from anywhere in the world can participate in mining without a centralized authority anywhere, right?

Please, educate me in this regard if you're able to do so. Why is it more decentralized to concentrate transaction verification into 3rd party groups of people instead of across the vastly decentralized mining community? Am I making any incorrect assumptions in that question and don't even know it??

It seems that the "centralization" concerns regarding mining pertain to 1) a single country hosting a majority of the world's hashrate and 2) a single manufacturer within that country dominating the mining hardware industry.

Is it not fair (and very decentralized) for this model to continue to proliferate? The code and protocols are solid, right? Anyone can obtain a miner and mine, right? And anyone can compete to manufacture the best miners, right?

I'm trying to understand why "China" is being blamed for capitalizing on the rules that have always been in place for BTC and why others insist now that the whole concept behind it needs to change. It seems, to me, that the real takeover is that attempt right there...

From a coding perspective, which I've been doing professionally for over a decade, the change of a 1 to a 2 is a lot less of an upheaval of what BTC is than trying to implement an entirely new layer in place of the existing code? Shouldn't the BTC code be updated only as necessary and 2nd layer solutions, such as segregated off-chain settlement, be done as a truly separate layer?

If a second layer solution operated its own code, its own coins, and was directly pegged to BTC without destroying the integrity of the current system in place.... what assumptions do I have wrong there? Why would this not be the most logical solution?

I truly am too ignorant in this space to come to my own solid conclusion. Someone, please, if possible, help me (and everyone else) out by providing some rational and informed perspective to the above thoughts and questions.

Thanks!