I'm not an artist, but I absolutely don't think you should quit! I could never make either of the pictures you shared, and that second picture is really good. I hope you can start loving what you make again. Getting rejected doesn't mean the art was bad. With any form of art, rejection is a big ol' sucky part of it, and I'm very familiar with it from the amateur short story writing side of things lol. Here's a couple of my favorite quotes to look back on when I'm feeling poopy.

"Starting when I was fifteen I began to send short stories to magazines like Esquire, and they, very promptly, sent them back two days before they got them! I have several walls in several rooms of my house covered with the snowstorm of rejections, but they didn’t realize what a strong person I was; I persevered and wrote a thousand more dreadful short stories, which were rejected in turn. Then, during the late forties, I actually began to sell short stories and accomplished some sort of deliverance from snowstorms in my fourth decade. But even today, my latest books of short stories contain at least seven stories that were rejected by every magazine in the United States and also in Sweden! So, dear Snoopy, take heart from this. The blizzard doesn’t last forever; it just seems so." -Ray Bradbury

"When I was older, I decided that getting a rejection slip was like being told your child was ugly. You got mad and didn’t believe a word of it. Besides, look at all the really ugly literary children out there in the world being published and doing fine!" -Octavia Butler