That's a subjective question.

If you devote your entire life to GameMaker, you might never pick up the skills you want, but on the other hand, you could spend years trying to learn the skills to code things from scratch before you're able to even start doing anything interesting with those skills.

I'd take a balanced approach. Mess around with modding tools, GameMaker, Unity, Unreal, etc. for a while and get a feel for what they do, how they work, and what you like about them. Play around with the high-level concepts of gameplay and game systems. You can then work on your own code once you have an idea of what kinds of things you need to learn how to do or what kind of tools you need to learn how to make.

Some of the better game-oriented coding school programs start out with kids learning the basics of C or whatever in one class while working with a tool like GameMaker in another class. to be a professional game developer you're definitely going to need to learn how to do a lot of things from scratch, but you're also going to need familiarity with how a real game is made, and GameMaker is not a terrible way to start that process.

Well, at the end of the day making games is the most important part of making games, so there's some value to making any game, and GameMaker does have its own scripting language. (And you can do some pretty robust things in it, like the original release of Spelunky.)

But if you specifically want to become a game programmer, as opposed to a designer, artist, or other development role, you'll have to buckle down and learn programming sooner or later. It certainly won't hurt you to learn with GameMaker, and having a gentle start might help you keep your motivation up, but it won't be directly transferable to AAA game development.

If you have some programming experience, you can check if there's some game libraries or engines in a language you already know. If you're an absolute beginner, but you want to jump straight to programming, I'd personally recommend that you look at Unity, because it uses C#, which is mainstream enough to have many outside resources for learning. Unity itself also has a lot of tutorials for you to start from. (You can also make 2D games with Unity, if you want to start with that.)

There are other options (like Unreal) but I wouldn't recommend them for a complete beginner because they expect you to be an experienced programmer right off the bat.

I'd also recommend that beginners avoid building their own engines at first. That may be something that you decide you want to do down the road, but learning how make a game and write an engine at the same time often becomes too overwhelming, even for experienced programmers.

Summary: Learning GameMaker won't hurt you, and can teach you about programming, but it isn't the fastest route to becoming a programmer.

If you are serious about making games, you will not find it as a credential for getting a games job. I believe Game Maker is a purely hobbyist tool.

If your resume says, effectively, "I once made a game no one knows about in game-maker, download it here to see how unpolished and buggy it is." then yes, its not a very effective credential. Nor will it ever be an effective credential if your aim is to become a graphics or engine programmer.

If, on the other hand, you can show that you brought to completion a highly-polished, relatively bug-free game that at least the people who've played it seem to enjoy, even if there's not all that many of them, then that's an excellent credential for many roles in the games industry. Not the only one you need, most likely, but it makes a positive note on one of the most crucial credentials -- the ability to make and ship something complete and polished, and possibly to take and implement user feedback.

Fully 60% of the top-grossing mobile games are made in Unity, which is not very far removed from GameMaker -- I daresay that anyone who can make a very complete and very polished game in GameMaker is fully capable of wielding, or learning to wield, Unity very effectively.

The novice-ness or not of the tool doesn't mean much for the kinds of credentials it speaks to. Yes, no one is going to hire you for your 1337 gamemaker skills and set you to work with it, but that's not the point. If someone can make something complete, and polished, and fun then it speaks to their ability to finish something non-trivial, and exercise the same kind of design skills any other toolset would exercise -- I don't care what language or tools you used, just show me something awesome.

Its not the whole picture of course, but neither are someone's 1337 C++ skills.