There are two available courses of action. Option one: We embrace something like DoH in order to avoid any possibility of blocking and detection. But you then have no simple way to back out from centralization if/when centralization (almost certainly, IMHO) slowly becomes a problem. Monopolies and oligopolies are hard to break once formed, and absolute power corrupts absolutely. Option two: We use DNS like always to avoid problems with centralization, and adopt a secure DNS protocol to avoid spoofing and unauthorized monitoring. If we do this latter thing, and detection and blocking does become a problem (and it might), we can always add some additional layer of security, like HTTPS tunneling, on top, which avoids it. We could even, if it became absolutely necessary, centralize after the fact; but this way, we can avoid it until it would become necessary.

I would prefer not to centralize things in advance, just in case a certain problem develops. I would instead prefer to keep it de-centralized as long as possible, and solve individual problems as they actually occur.

I would also prefer DNSSEC and DoT over DNSCurve, and I would suggest IPsec with opportunistic encryption to be a more pure goal than to tunnel everything over HTTPS, but my preferences in protocols are not important to any of these points, and we don’t need to argue about that.

We're already there. There are already ISPs in some parts of the world redirecting DNS queries to any DNS server to the ISP's DNS server, which gives invalid responses to queries that authenticate the DNS server (DNSCurve) or invalid responses to queries it can read and wants to block (DNSSEC), either of which is an effective denial of service attack. Which drives adoption of ugly DoH.

The root problem where the centralization comes in (because you could actually do DoH to something that isn't Cloudflare), is that you need to trust someone to faithfully and completely answer all of your DNS queries without dropping any of them or sending invalid responses for queries they don't like.

That used to be your ISP, and we had a decentralized solution as long as the ISPs would faithfully answer all queries, but what happens when they don't? You need someone else. "Let everyone choose for themselves" is a theoretical answer, but in practice the average person doesn't know anybody who runs a public recursive DNS server, and Google and Cloudflare are easy and "free", so everybody will end up on them. To prevent that we need ISPs to stop interfering with DNS.