Harvard has gained a reputation for focusing on research more than educating their students. Undergraduates are particularly neglected. However, I’ve heard that the situation has gotten better over the years. Can anyone tell me if undergraduates suffer from lack of attention or opportunities at Harvard?
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.
I agree 100% with what @gibby says, but I want to add some color to it.
- No one, or hardly anyone, at Harvard or any equivalent research university -- Harvard isn't unique at all in this respect -- gets hired or gets tenure because he or she is a great teacher. They get hired because they are great, influential scholars. Some great, influential scholars also happen to be great teachers, too. It's not by accident, exactly -- some of the things that make scholars influential include clarity, charisma, and communication skills, and those qualities help teaching, too. But there are plenty of great scholars who are not so great teaching introductory lecture courses, and that's where Harvard (like most of its rivals) gets its negative reputation. When you get into more advanced classes, students have more background and more focus, so they can appreciate what makes a great scholar great. That's where you really get the benefit of Harvard's faculty.
- What advances the career of a Harvard professor is producing research and scholarship, and mentoring fabulous PhD students, not explaining to undergraduates for the fourth time what's going to be tested on the midterm or listening to them whine about grades. The graduate students they are advising (a) are effectively their more-than-full-time employees for a number of years, (b) work around the clock to understand what interests the professor, (c) help the professor produce scholarship and enhance his or her reputation, and (d) are in a lifelong relationship with the professor. Also, when the President, or a Cabinet secretary, or the New York Times calls, the professor is going to take the call. Undergraduates can't really compete with that, and it isn't worth trying. What undergraduates can do is fit themselves in to a particular professor's ecosystem, hang around, and learn stuff if they put in the work. That's a skill you have to cultivate if you want to have a relationship with faculty as an undergraduate at a research university.
- Something that is somewhat unique to Harvard: I don't know of any other similar college where the average student spends so little time and attention on classes relative to extracurricular activities. That's not true of all Harvard students, but year after year Harvard seems to select for students who are likely to behave that way. If Harvard professors seem to care less than they should about undergraduate teaching. it's due in some significant part to Harvard undergraduates seeming to care less than they should about classroom learning.
I agree with @gibby 100 per cent also. However contrary to what @jhs said there are some professors at Harvard who get tenure because of their teaching ability. For example Malen with CS50 is a full professor. His class is legendary. I don’t think he does much research at all. The same can be said with Blitzstein in the stats department. He is a great teacher . Mankiws econ class has about 700 students and he also does a lot of research on the other hand
While both Malen nor Blitzstein are regarded as excellent lecturers, neither is a full Professor; they are Professors of the Practice. This is not a tenured position, but rather a 5 year appointment with options for renewal. It’s a distinction that few outside of academia care about, but it’s there. Just like the majority of people will not know the difference between a TF and a TA.
Mankiw is a full Professor and does research. His text Principles of Economics is widely used and must be paying him a boatload of royalties since he had no qualms paying $2500 a ticket for Hamilton. 
@collegedad13
https://www.nytimes.com/2016/10/23/upshot/i-paid-2500-for-a-hamilton-ticket-im-happy-about-it.html?mcubz=3
This is very outdated. In fact, undergrad life has been a real focus in recent years, not only academically but in terms of dorm life and common social spaces.
Harvard has a system whereby lectures are given by professors and grad student teaching fellows lead “sections” for discussion. TF’s/TA’s are common at many universities. If you want a class taught entirely by a professor, look at liberal arts colleges or ask questions at the universities and colleges you visit.