I'm not sure if you're being sarcastic, but it means nothing to "own" the browser when, realistically, you're going to be playing catch-up with the whims of the one corporation that basically controls nearly all decisions on the spec.
The spec only has the power it does because of the market share of Google’s browser though. More people using independent browsers means less power by google to single-handedly control the spec.
Basically noone other than browser vendors will look at the spec anyway. The reality is effectively descriptive, not prescriptive.
Sure, without having a majority marketshare a browser can't by itself push for their new features to be supported by other browsers, but they will effectively disincentivize website owners to not use features they don't support if they have marketshare of any significance. At which point it'd be in W3C's best interest to allow Ladybird to participate, or else their work gets underutilized.
