It saddens me to see that the debate over whether an author should know grammar and how to spell never ends. We do need it, is because it allows the thoughts to flourish, and the established standards do that. Yes, grammar still matters. It never stopped being necessary. Art is expression. Grammar and structure are part of the brush and canvas.
The meaning, the feeling you want to convey, is only understandable when the stucture is correct.
Spelling is less of an issue, if one at all. Spell-check on a PC and done. Grammar, though, has its own importance. I can get the idea of a sentence if the words are spelled wrong, since I can guess at context. But if the grammar is wrong, then I cannot be sure of what the context even is!
Paint with a brush, draw with a pen, write in proper syntax.
152 words wasted outside a novel.