A new web-centric OS could fix those issues by doing a few things to reduce friction.
First, use an Android-compatible kernel version so drivers are easy to port. This gets manufacturers on board.
Second, make your App Store a non-profit that charges enough for ongoing store development and distribution. This gets devs on board.
Third, make sure you have decent third party framework support. Flutter, react native, and maybe even an Android runtime that legacy apps can integrate into their wasm binary. This helps kickstart your ecosystem.
Fourth, add better integration of webgpu and 2d canvas (which probably needs some extending). In addition, they need to add a low-level API to access DOM nodes from wasm. For security and ease of implementation (without stepping on the toes of the normal standardization stuff), this would probably be a virtual DOM with only a provably secure subset of the actual nodes being sent back and forth.
UI is an easier problem. The best design to date is still webOS. Copy their general design (maybe rip off some of their never-shipped mochi stuff).
The biggest issue as you said is financing. All these things turn into lots of developers and time. The best bet here would be replacing something like Tizen where a corporation is already investing.