Similar Image(s) Already Submitted / Quality Issues

I've been uploading to this site, along with several others, for many years and there seems to be a recent tightening of the review process.  I shoot professionally and can spot no reason for most of my images being suddenly rejected.  It has to be frustrating for newcomers if a long-timer like me is getting tired of it. They're starting to behave like Shutterstock, which I stopped uploading to several years ago.  

There is a long thread about that here in this forum. Adobe uses a new tool to check new assets against the whole database, and I suppose, they are overdoing.

As for your quality rejections, they are probably real quality issues. I don't know what specifications you think that are applicable, but check your asset at 100% for artefacts. You will most likely find many of them.