With all due respect, I am an artist and I do understand constructive feedback. I value constructive feedback immensely and it has helped me grow so much over the years. But I also believe that constructive feedback should only ever be given when solicited. Even though it can still be valid when unsolicited, it doesn't make it appropriate, and in the case of OP just wanting to share their work, it certainly isn't. It's like telling a coworker that their outfit isn't working for them. That may be valid and helpful, but even if put nicely it's still inappropriate.

That said, the "critique" given wasn't even valid. Like I said, it was an entirely aesthetic critique that wasn't based on anything technical. There's a difference between "The anatomy on the left arm is slightly off" and "I would have used watercolours instead of acrylics": one is based on good technique, and the other is purely preference. And it's generally safe to assume the artist isn't interested in brainstorming ideas with viewers.

Sorry for ranting, but I generally just dislike when people give unsolicited critique when the artist simply wants to share their work. It's just basic artist etiquette.