Can a Book Publishing Company Really Make a Difference?

I’ve been exploring working with a book publishing company but I’m curious do they truly help authors succeed, or is it mostly a traditional route with limited impact? Some writers say a reputable company provides editing, design, and marketing support that makes a real difference, while others claim self-publishing offers more control and faster results. For those who’ve partnered with a publishing company, did it significantly improve your book’s reach and success, or could it have been done independently?