If you're writing in first person, I'd advise against dropping a bunch of appearance stuff off the bat and instead drop it in more casually. For example, if they have a sibling, something like "we have the same thick, dark hair", "she has a few inches on me, even though she's a few years younger", or "my younger brother has blue eyes, the only one besides my mom who does" can offer a way to describe them while also giving you a roundabout way to describe your protagonist. Sprinkling in some comparisons and contrasts to other characters gives you space to describe the MC without bringing the story to a halt to do a paragraph about their looks.
For third person stuff, you have more room to work with and I honestly feel like it depends on the character? Like you don't want to spend as long describing a random side character as you do the love interest. I will admit that I do tend to indulge in fairly in-depth descriptions for some third person, but I make it work with the writing style I'm using and the story I'm working on–my fantasy stuff does this more than my realistic fiction because, generally speaking, a fantasy setting allows for more fantastical language and descriptions, and I use a more formal style. Don't drop everything about their appearance at once or describe them to the point where it brings the story to a halt, and make sure that it fits the character who we are seeing from the perspective of, if it's in 3rd person limited.