After some procrastination, I finally finished Death Stranding 2 over the weekend. My thoughts overall are complicated, but it's Kojima at his most bombastic. It's a unique piece; some of the ideas are so far out there, I can't imagine anyone but him being given the budget and time necessary to see it through.
Overall, having played both back to back, I'd say the narrative is stronger in the first game. The sequel has higher highs than the first, but it's more inconsistent. The gameplay in the second is best-in-class. It feels like the logical continuation of what was started in MGSV, which is why I've heard that it's so MGS-like. You have a large sandbox of toys and you get to choose how you want to proceed. Also, DS2 took a good look at the UI in DS1 and corrected pretty much every issue I had with it.
All in all, I'd say DS1 is absolutely required reading before playing DS2. The games are waaay too interlinked to skip it. For the future, there is a very obvious thread to pull on for another game, but so much of what was built in the first two games is over that you'd really have to take things in a different direction. I'm curious about OD, but I'm more interested in seeing what PhysInt is going to be.