OMG, so much wrong here. You should really do some research on Cardano. And also not every PoS is created equal.

“PoS inevitably leads to centralization and requires an inflationary currency supply. That is the problem. Coins in transit can’t stake.”
Cardano actually has native liquid self custodial staking. Your coins NEVER leave your wallet or are locked (unlike Ethereum for example). You can freely move and send coins while you are staking your wallet. It is true that stakers are paid with inflation. But the same is true for Bitcoin. When inflation dries up, they will be paid in fees. Cardano also has a capped supply like Bitcoin (45B), unlike Ethereum.

“You are paying those stakers with an inflationary supply. Which means you are minting new coins and handing them to users who already have the most coins. This leads to centralization of the supply over time, and therefore, control of network consensus.”
This is another common misconception about Cardano. For example, in Ethereum only a small fraction of ETH is staked and yes, inflation and fees go to owners of that small fraction of ETH. That’s because ETH has very bad PoS with slashing (risky to stake), locking (inconvinient to stake), no native delegation (hard to stake for small users) etc. In Cardano, about 62% of all supply is staked - because it’s risk free, a no brainer essentially. And the rest of the supply which in not staked is actually mostly huge whale wallets. In Cardano inflation and fees don’t go to just the rich, they go to EVERYONE. If you have 10 ADA or 1M ADA you both get about 3.5% new coins per year atm. That’s probably another misconception because people think “Ethereum staking bad therefore all PoS must be bad and centralizing”. In Cardano the network actually seems to be decentralizing, lol. In the past few years, about 20 pools had control of 50+% of block production, this has slowly but surely increased to over 30 now. And by pools I mean actually independent pools and not like in Solana 1 entity with like 10 pools. For this stat in Cardano all entities with multiple pools are actually counted as 1, and still we are hovering in the 30s, and even Bitcoin is at like 2. https://cexplorer.io/groups

“A few rich, powerful people end up controlling the whole system, just like our existing banking system. No thanks.”
This is not the case with Cardano and it seems likely, as I said it’s actually heading in the opposite direction.

“Most of those PoS chains also have massive chain sizes/system requirements compared to Bitcoin, which means they can’t be or remain nearly as decentralized, neutral, and secure.” Yes. Luckily Cardano is different and we are at 151 GB. Cardano takes this seriously. We have a pretty small blocksize and tame node requirements. I think most of your grudge against PoS is because you instantly think of garbage like Ethereum or Solana. You probably dismiss Cardano because there has been HUGE anti Cardano sentiment from pretty much the whole crypto secor, be it Bitcoin, Ethereum, Solana or others.