The smaller the company, the less likely the hiring process is a well-oiled machine, from responses to inbounds to true-ing up the JDs currently advertised on the site; compounding that, smaller companies get fewer inbound applicants and can end up holding out for a unicorn fit for a role for a long time. I wouldn't read much into no-response from a startup (totally reasonable to be irritated about it, but it's always a numbers game regardless, so you might not want to be hanging on a response from any one company).