If you're comfortable coding, JupyterLab lets you work in Python/Julia/C as you prefer and you have access to a vast ecosystem of library support. I'm constantly amazed by and grateful for the whole SciPy ecosystem and the Numfocus project.
The downside is the sheer range of options makes for a very steep learning curve and things like interactive widgets are overly complex for students or new programmers. But once you get going Jupyter notebooks are a very pleasant environment to work and sketch ideas in, and they're so well established for scientific and educational use that you don't have to worry about them falling out of fashion.
Mathematica is still very slick and a really good product, I could just never get with the proprietary aspects of it.