Or another way to think of it is, "who is the competition for?"
Ignore the dangling participle
Seasteading and spacefaring are proposed as means by which the human species can better sustain its growth and perhaps even mitigate its impact on the ecosystem. However the concern is that, while this is a true argument, it isn't a guiding principle for the legislation cropping up around the technology which makes these futures possible. Specifically the concern is that the ultra-rich will use these technologies and permissive attitudes towards "uncharted territories" to essentially establish sovereign nation-states (or mini-states, communes, enclaves, etc.) under which they have total authority
Are you prepared to live in a future of Amazonville and Musktopia?