C3 is the most used engine on itch.io. It IS already successful... GameMaker has been around literally decades longer and therefore a you'll find more stuff of it online and not everybody NEEDS the level of ease of use that Construct offers. Some people want to code traditionally, especially if they have a programming background. And yeah if you want to do 3D then of course you'll go with Unity or a similiar tool.
And tbh if i would be a GameMaker user for the last ten years then i would be VERY weary of learning anything new vs. just making my next project because i'm simply just used to it. Not because GameMaker is inherently better but because i would already know how to use it. In the end it's about making games not endlessly deliberating on engines.
Now Construct has its own wrappers too that allow for lightweight apps on Mac and Windows.
As for Consoles: every Unity dev i know who released a game on console worked with a publisher who did the ports for them. I think people underestimate the enormous complexity involved with publishing to these platforms. Construct has two publishers/porting houses that i know of: Ratalaika and Chowdren. So it's not really an issue.
In the end, it comes all down to personal preference. That's why there are 100 flavors of Pringles and not just one. Same with game engines.
And from what i can see, Construct is growing steadily and already a pretty big player in its range. Like the GMS2 CEO once said, he doesn't see himself in competition with Unity at all because they are targeting different types of developers. And the same is true with Construct.
So just keep using it as long as it suits your need. BTW, nobody sais you should only learn one tool. I know many people who use Construct next to stuff like Unity etc. I personally i.e. use THREE different animation apps (Toon Boom, Moho, Grease Pencil) depending on whatever job i have to do and which one is the strongest tool for that. So yeah, there's my 2 cents.