13eck amd b1 are sooo right about previewing the instructor !! I made that mistake with a udemy course where the content was great , instructor simplified and broke down concepts well, the course had crazy good reviews ; but something about the instructors voice was so incompatible with my DNA- it was physically uncomfortable to hear his voice , I have no idea which attributes of the sound (pitch, tenor, vibrato, etc) were so incompatible for me. Just bizarre how deep the discomfort went , like on a molecular level.
So random and disappointing but just wanted to share a testimonial of why that's such an important step to consider. Have run into the same thing with some other YouTube creators where I cannot consume their content, no matter how good the quality because of the sound of their voice.