Read CTR next to impressions
Click-through rate is clicks divided by impressions. YouTube will show a video more widely over time, and CTR often falls as it leaves your warm audience and meets colder ones. A drop in CTR after a video travels is normal. A low CTR while it is still being shown to subscribers means the package is unclear.
There is no universal "good" CTR. A niche tutorial can live at a lower CTR than a drama thumbnail and still be a better business. Compare your videos to each other.