It's a tool like any other. It has a place and a use in context.
They're definitely antiquated, though. You mention superheroes but even they don't use thought balloons for 20 years now. The thought balloon was, as people in the thread pointed, substituted by square CAPTIONS (which is the name you'll find for them in DC/Marvel script samples around the internet). Originally they were used solely for the narrator's voice, but not for a long time now. That's the more modern alternative.
That said, of course you're allowed to use them. You can do anything if you think it serves the story you're telling! I unashamedly use thought bubbles A LOT in one of my comics here on Tapas. It's a superhero strip based on, among many things, 60's superhero comics. In this context, it works for me. Not saying I did a good job with it, but I tried haha
As for restrictions, I agree with what was said. The worst thing you can do is use them to describe something you can show (although even this can work in context, right?), but they can certainly give insight into elements around.
But yeah, it all depends on the story you're telling, the style, the mood, the storytelling. Anything can work in context!