How to get a list of entities programmatically?
From the very beginning, I went the wrong way. The problem is solved with the vievs_rules module. I made a view of simplenews subscribers, with relations with subscriber:email and subscription:category, then added filters by term (subscription category), by user (active or not) and subscription status. I used a user entity as resulting variable. Then I just imported the view into views loop (Rules UI) and voila!

Very thanks to @Pierre.Vriens for pointing me to views_rules