I guess it didn't strike me as introducing time-travel. I assumed based on Pennywise's (It's) origins that they indicated that It was more "omnipresent" in each of the timelines- like an old god etc (aware of/experiencing past and future simultaneously). When he said the Losers would bring about his death "or maybe 'his' birth" he couldn't tell anymore, it struck me as non-linear time experience. Almost like he is present in each timeline simultaneously, every action in one has a reaction in the other that ultimately causes the same outcome- like a nasty trap that continues each cycle no matter what It does. I thought that was an intriguing way to connect the lore/storyline across multiple cycles. I'm excited for another season of easter eggs that will further delve into the history of Derry and the deep rooted origins of the Losers- because I think that's part of why they succeeded. Plus Stephen King is known for his complex universe building- the connection to Dick Halloran/The Shining was a brilliant link to greater works and opened the door for even more links across Kings literary landscape.