Yes. Investment banks hire some candidates who simply apply online, particularly when those applicants have strong academic records, relevant experience, and clearly presented résumés. Formal recruiting processes exist for a reason, and networking is not an official requirement at every firm.
However, submitting an application without making any contacts leaves more of the decision to résumé screening. Recruiters may review thousands of similar profiles, so even qualified candidates can be overlooked. Networking cannot compensate for weak qualifications, but it can help someone understand your background and recognize your interest before interviews are assigned.