Is 2D animation still relevant?

Yes. Now studios are combining 3D with 2D. A studio I worked with did projects using both 2D and 3D.

2D is still a very big part of animation and will be around for many more years to come.

I'm a writer rather than an artist, but I've worked in comics, animation, and videogames for decades. I've worked closely with many different types of artists. I'll give you some guidance, and hopefully some animators will add more guidance.

You asked a second question having to do with using MAYA, and whether you could be a 2D artist without having to be a 3D artist or master technology. Consider this an answer to both questions.

From the way you phrased your questions, you want to be an animation artist as a career and earn a living at it, which is different from doing it purely as a labor of love. There are many animation artists around the world who turn out short 2D pieces, enter them in indie film contests, or simply put them on youtube. You could certainly do that, but you probably wouldn't make a living doing it. It would be very, very difficult.

So, setting that aside, if you're looking for a genuine career that supports you, you will be crippled if you only know 2D techniques.

Your major career markets as an animator will be: TV, film, and videogames. 3D animation dominates these markets. Advertising might offer a fourth market, but it isn't as significant a market. In videogames especially, it's 99% 3D.

Any of these will be tough to break into as an animator, and you'll need good 3D skills.

And now matter what type of animation you go into, the single most important thing you need to be is a terrific artist. That means having top-rate drawing and illustrating skills, as well as technical skills.