It's reasonable to not do in-depth research on every company you apply to during a job search (though some would argue that the smart applicant does exactly that and applies to far fewer jobs with a more personalized, targeted approach).

It's completely unreasonable to walk into an interview without having the foggiest idea of what the company does. This isn't complicated; take an hour or two before an interview to learn about the company, the competitors, and the space in general. Yeah, you might get hired by someone without doing that, but you're at a disadvantage against other applicants who understand that "talented" isn't enough.