What to do if most of my students have switched to a better lecturer's class?
You should discuss this with your department chair (the person who runs your department). While the teaching chair (or graduate/undergraduate chair) might seem more relevant, it is the chair of the department who you have to keep happy. Their opinion matters more than ours.

Describe the dwindling number of students as a concern, then see where the conversation goes.  Instead of offering your suggestion, invite your chair to offer their thoughts and suggestions first, before you launch into yours.  Who knows?  Perhaps they will suggest closing down your section on their own and you get what you want.  Their response probably also depends on the attractiveness of your research alternative versus their need to find instructors to cover sections they've already committed to offering.

Your chair may also be glad you invited the conversation, because they may have some feedback based on their own observations and conversations with your colleagues and students they would like to share with you.  They may be able to tell you how you could get better so you could one day be the instructor who draws away everyone else's students.

But I agree with and upvoted DBB's answer, that trying to dump the class could make you look bad and that if you care about getting good at teaching, you should simply "push through" and deliver the lectures.