For drag and drop game making, Construct does not lag behind GM at all. It's much more logically organized, and the runtime is much MUCH faster and more powerful. As far as drag and drop is concerned, the only way in which Construct lags behind GM is this:
And...that's about it. Anything else, such as "GM can do online" or "GM has a large userbase to get support from" or "GM can use gamepads" or anything like that... Construct has plans for all of these, so it's just a matter of time.
Yes, there are lots of things that GM can do that Construct can't, but you have to dig into GML to do them. Like 3D, or using .dlls.