There's value on the wrapper around the rendering engine. Presumably you don't use the raw engine, and use many of the UX features provided by your chosen wrapper (of which there are many). Things like tabs and extensions, hell even having history,
settings, cookies, and a back button are UX niceties a raw engine doesn't necessarily provide. So the wrapper is important; making a better wrapper is thus a worthwhile endeavor. Extensions only go so far, and if ManifestV3 ever lands, and stops ad-blocking extensions from functioning, it's easy to see a hypothetical consumer-focused browser that restored that functionality, or had it natively would easily be worth millions.
The only question is if they can actually make money, and the kind of money that VC investment demands at that. Opera, the browser company had revenue of around $380 million last quarter, but if you don't use their browser, which is also "just" a chrome wrapper, you'd never know it.
To put it another way, Linux distros; Red Hat, Debian, Ubuntu, Arch, etc, are all "just" wrappers around the Linux Kernel. Yet "I made a Linux Kernel wrapper" is worth at least a billion, in the case of Red Hat. If you never come near that distro, you might not even see a reason for its value, but you can't argue with their sales numbers.
