Hmm, I don't mean to be the classic fence sitter here, but for me, there needs to be a balance.
When I was blogging at Livejournal, I wrote for myself. That was years of writing for myself. It enabled me to develop a unique voice in my writing, which is something I'm really pleased to have. I also have some amazingly honest entries to look back on, and it's quite fascinating to see my point of view as it was then. Looking back, of course, we have a different view of things. If I'd been writing for an audience, I don't think I'd have the same blogging voice. By blogging in what was essentially a vacuum for so long, I know that my style is...me.
While my blogging evolved (maybe not into anything advanced, but it evolved dammit!), my poetry and short stories did not. It wasn't until I came to Writing.com and started getting 'audience feedback' (also known as reviews) that my poetry and short stories started to improve. And before you question whether they needed to improve, yes, yes they did. I had a very simple style of writing, and I honestly wasn't satisfied with my writing. I wanted it to be better. I wanted to be able to express myself better in those mediums. I love some of the pieces I've managed to create in the last seven and a half year. Woah, has it really been seven and a half years?! That's insane. So while not everything I write is amazing, I know that some of my favourite pieces, and some of the pieces I'm most proud of (not always the same thing) wouldn't exist if I hadn't had that audience feedback.
Ultimately, we're all in this for a selfish reason. Some of us want fame or fortune from publishing or becoming the next blogging sensation. Some of us want an outlet. Some of us want a hobby to occupy or entertain us. Some of us want to learn skills that can be put to use in other fields. Some of us want to educate. Some of us want to record our lives for prosperity. Many of us want a combination of things. No one writes because 'it makes my mum happy'. Or if you do, you're unlikely to stick with it. We do this because we have a selfish motivator one way or another. So ultimately, sometimes you need to be selfish and stay true to yourself. But unless it defeats your entire purpose of writing, why not find the balance that works for you? Take the feedback that works with your style and leave the rest. And while I'm no all-knowing guru, I think that you'll find you can grow and learn, and still stay true to yourself.