What do you think of No-Code Development?

Just like the title. What do you think of no code development tool like bubble.io ? I already hear of it this past months but only today I actually look into it. It's look good for easily designing the website but what about backend? It is good ? In what languange it was using in the backend? Is there any security issue ? How fast is it ? I was thinking of trying it so I need your insights if it is worth the time ?