If as the OP said, the whole population of earth. ~8 billionish? were instantly transported to an alien world with zero tech to help survive. (this is a question within itself! and wouldn't mind seeing a question on it) how many would survive the first day (immediately dying from lack of shelter)? 3 Days from the lack of hydration. 20 days (weakend to the point of exhaustion from lack of food). Past a month no bets. Interpersonal and intergroup conflicts I can't even begin to assign an attrition rate. Disease from unknown viral infections, Not to mention how many would perish from god knows what in the first 15 minutes after the ... BAMPH!
All this considered, with current world population, an even more technologically entrenched population from the future would only make it worse, a 20% survival rate IMHO is generous. Around ~1,600,000,000 That's about the same as earth around 1850ish and perhaps 14 pop/km^2.
Point being, losing 7.5 billion people in so many days is gonna leave a mark. Visceral survival instincts will kick in and no one will give a damn about anything other than their next meal and who is going to stab them in the back or who they can stab in the back to live another day. If anything meaningful at all is remembered past one generation (significantly shortened lifespan generation!), outside of an isolated extraordinary individual, it would be surprising.