I disagree with most of the complaints. I feel like these assets are well worth the wait as well. This is just how some artists work. Some of us suck at timeframes, too. But, Mega Tiles always come back eventually with excellent quality work. Also, great opportunity while they're not here to practice your own pixel art and try to make your own custom sets for this software.
I get that it sucks to wait for stuff, especially when the person you're waiting on might be bad at communicating realistic timeframes. But have faith, Mega Tiles usually pulls through.