A short answer: it depends on what kind of person you are. It also depends on what kind of class it is. It depends on how good of a lecture the professor is, too.
A long answer: A common argument against attending lectures is that one can learn more efficiently by reading books / studying class notes. This is true in certain cases but comes with caveats.
Think about how you are spending the time you gained by skipping a lecture. If you are actually reading class notes and books and learning the material (except taking half as much time), then that’s fine. For me, this was hardly ever the case. I would hang out with my friends (who I believe also skipped their classes) or watch stupid YouTube videos to pass the time. And hours before a problem set deadline or midterm, I would try to cram everything in my head. Grade-wise, this method had varying degrees of success. Learning-wise, it was a horrible idea. Most people don’t learn well when they cram. Yes, there are a handful of people who can do this. Chances are good you are not one of them. So, if you don’t have the discipline to spend time regularly to stay on top of your class while skipping lectures, go to your lectures. After all, you are paying for them. And if not for anything else, lectures remind you regularly that you need to read / study for the class.
Actually, on the topic of bad lectures, I used to think they were pointless and a complete waste of time. A bad lecturer teaches you what NOT to do when you are speaking in front of a large audience. No, don’t go through 200 slides at the speed of light. No, don’t dive into an abstract concept without anchoring it on concrete examples. No, don’t go overtime just because you failed to time yourself accurately. Lecturing is hard, and many of the bad lectures that I attended made me think a lot about effective public speaking and presentation. My only point here is that even bad lectures have merits. So, you should go to bad lectures too, at least a few of them.
Attending lectures, especially in small classes, is a great way to put yourself on the professor’s radar. Trust me, if you have any plans to attend graduate or professional schools, you want at least a few professors to know you well, both academically and personally, so that they can write meaningful reference letters.
Finally, some lectures are just fantastic. I can name a few classes that blew me away and altered my thoughts and world view forever. After college, you do not have that many opportunities to have leading experts share their insights and ideas. Make the best use of these opportunities. It goes without saying that the only way to find out who is a good lecturer is attending lectures (or have your friends attend them and report back to you, but even then, your friends and you might have different ideas of what constitutes a good lecture).