Quite frankly I have not been using click cards, in my mind it feels they would take the viewer’s attention away from the video. I do agree with everybody end screens are valuable and worth the effort.
I've been looking at my analytics data for cards and the click-through-rate for cards is very very low. It does seem that people see them as an annoyance. The click through rate of endscreens is much higher despite coming AFTER cards in the timeline of a video. I've almost come to the conclusion that taking the time to add cards isn't worth the effort.
Endscreen videos are important to include as they do more than you might think. First they feed the Youtube more meta data maybe? 2.They make your content potentially more discoverable as Youtube may promote it more (more impressions). Why?.. because it will gain more watch time if the viewer is watching another video afterwards. 3. err same as last half of '2' You get more watch time! .4. I've forgotten no.4 But I'm sure it would have been very wise! 5.Use a playlist rather than a video endscreen as has potential for a binge watch.. although experiment as I find video endscreens have greater CTR than a playlist.
Oh and it really don't matter what you do with cards as hardly anybody ever clicks them in my experience. They are best used if they are worked directly into the video narrative with a purpose.. rather than just a card pop-up suggesting a random video for no given reason. For example I use a Poll card question in my signature video below which asks viewers to vote which speaker sounds best. Thats the only card from all my videos that gets any proper engagement.
As with any tool or method, it should be used appropriately. Popping up random cards is annoying. Use them effectively. As for End-Cards, it is your last opportunity to connect with your audience. Since YouTube rarely presents recommended videos from the channel that you are watching in the recommended sections, if the viewer watched until the end, they may want to watch another one of your videos. Plus, you can use the 'subscribe' card!