Not only are you allowed to step away from the constant flood of global news, you NEED to. You HAVE to. Humans are not designed for having tragedies and horrors thrown at us constantly and with no break, we aren't designed to be overwhelmed with the awfulness of things happening across the world that we can do nothing about. Never giving yourself a break, and GUILTING yourself for even wanting one, is going to kill you. It is going to destroy your mental health, your ability to see any good in the world and in other people, and your motivation to do anything.
Burning yourself out by refusing to look away from horrible things you can't stop is not activism, it's just going to completely burn you out. There's a reason why individual leaders in activist movements focus on extremely specific things and not on everything bad happening in the world, and those are people with years if not decades of experience with caring for themselves while involved in activism. Show yourself some kindness and step away from the news feed.