Why shouldn't quality issues not be part of illustration rejections? You need to read the manuals. There are a bunch of things that you can get wrong with vector graphics.
Your illustrations look like bad photographs, where you applied some kind of fancy filter and then did a bad job cutting out the bee and flower.
This is probably not the kind of art that Adobe stock looks at. I'm sorry, but even if the cutout job had been perfect, this would have earned a refusal.
If you are new to stock, you should consider these resources: https://helpx.adobe.com/stock/contributor/tutorials.html
Please read the contributor user manual for more information on Adobe stock contributions: https://helpx.adobe.com/stock/contributor/user-guide.html
See here for rejection reasons: https://helpx.adobe.com/stock/contributor/help/reasons-for-content-rejection.html
and especially quality and technical issues: https://helpx.adobe.com/stock/contributor/help/quality-and-technical-issues.html
