DoH does not imply centralization in any way. Any trusted party can provide their own DoH endpoint. I can run my own DoH server on a cheap VPS hosted in another country.
I live in an increasingly oppressive regime. Most of the blocking is done at DNS level. DoH is a great solution. Slamming DoH because they can anyway spy one way or another is a poor argument.
The issue is each application implementing DoH themselves. Now any software which you wish to use your own DoH resolver would have to be configured individually.
A better solution would have been for Mozilla to fund development of an enduser friendly DNS proxy application which would enable DoH system wide.
The ideal solution would be something that can be installed in any home router, but that's a non-starter because of total lack of home router configuration standards. Flashing a router is not user-friendly for anybody.
The next best solution would be your suggestion, but that too is not practical unless it comes preinstalled on all OSes because the average user won't even know they need something called a DNS proxy. I don't see OS vendors agreeing to preinstall it. Additionally, AFAIK, popular OSes like Android and iOS prior to some versions don't even allow such system-wide DNS proxy configurations.
The practical approach left then is to implement it in browsers, solving it at least for the most common use case on all devices. Everybody knows how to download and install and use browsers. In a discussion forum I frequent, average users ask for ISP censorship bypass solutions all the time. Since Chrome does not support DoH yet, among all the possible solutions - VPN, Tor, SSHproxy - using another browser is actually the most user-friendly, least expensive, most performant option. It helps that it's Mozilla's product because their trust perception is higher than Google/MS/Apple/VPN providers.
I feel Mozilla's taken a good approach overall within the scope of their area of expertise.
DNS-based censorship doesn't work well enough for governments to be useful, it's always just a first step towards much more aggressive censorship tech. You should not advice people to use DoH to circumvent censorship, Tor is a decent longer term solution, and so are private VPNs, proxies.
Although I find it suspicious that there is just DNS filtering on your ISPs side and no IP filtering. Is it at the stage where it's not even enforced, semi-voluntary censorship by ISPs? Otherwise once the government starts checking compliance it will force IP-based filtering too, where DNS filtering circumvention is useless. And governments don't care about how broad the filtering is. Russia, for example, blocked half of the internet once in an attempt to censor Telegram.
It is semi-voluntary and I don't think it's enforced for now - not heard of any end user getting punished by government for circumventing.
DoH is a simple solution that works for now.
TorBrowser takes it to the other extreme - it's a good secure solution (I think), but not required as of now, and seen as slow with plugin and other usage restrictions.
VPNs, proxies are not seen as good solutions because people prefer free to paid, and they are not as trusted as CF and Mozilla.
Self-managed VPNs/proxies are not easy for the average person to setup.
I live in an increasingly oppressive regime. Most of the blocking is done at DNS level. DoH is a great solution. Slamming DoH because they can anyway spy one way or another is a poor argument.