We are facing highly soft rejections with themes as the WordPress standards are I think updated very fast.
I think there should be a document or forum where we all new WordPress standards should be stated clearly.
Any comments or feedback will be highly appreciated.
Are you kidding!
It is long & hard work to get these standards for Envato Marketplace. There is just ONE rule “Do good and good will”.
NEW Envato authors have a real problem with it, but that such is a Life BABY.
Mass. for all authors “Do you need help for pre-reviewing your WP, HTML … item - get in touch to me!”
Self promotion 
You should read a few admin reviews from .org, they apply the same rules. One of the reviewers on Envato’s team is also an admin there.
You can then make a list of the common issues.
https://themes.trac.wordpress.org/query?priority=!theme+update&status=approved&status=closed&resolution=live&changetime=30+days…&group=owner&col=id&col=summary&col=changetime&col=resolution&col=priority&col=status&col=owner&report=25&order=priority