First, will a new project make a difference? If the problems of artwork and marketing - especially the latter - remain unsolved. ( I'm in the same condition and I won't draft a second app.)
Second, people say ads would be a lot of money. But if you can only get $1 back for $100 spent, what's the difference if you spend $1,000,000 ? Only to get 10,000 back? Anyone with experiences?
Perhaps no one replied here has the real experience of struggling out in the same condition. Provided that, all the suggestions could be misleading, you have to think for yourself. Anyway, good luck.