Your information is inaccurate. ALL Harvard professors – even the noted ones – teach undergraduate students and have open office hours. That said, Harvard professors are often heard to proclaim “very few students show up to those office hours” – so it is really up to THE STUDENT to take the initiative, but if they do, Harvard professors are more than willing to meet them halfway. If an undergraduate can ingratiate themselves with a Harvard professor, then that student is golden! In other words, the professors welcome undergraduates to research opportunities, but they wait for students to make the first move. So contrary to your post, undergraduates DO NOT lack for attention or opportunities.