Pretty good review!
I've not yet been to all the new planets. What I have seen lines up well with the characterization of Wube strategically disabling the things in the base game / on the starting planet ("Nauvis") that I grew accustomed to. Instead of simply adding ever more lengthy production line recipes, they have forced us to approach many existing production lines in a drastically different way.
In the base game, you can play around with ratios and targeted throughput, but you almost always will have the same machines crafting the same recipes, in the same order. The most significant decision when designing a production line is often whether to bring an item in by belt or instead bring its components and craft it adjacently.
Space Age shakes that up by introducing several new choices/decisions to make. There are alternate recipes to be unlocked (similar in function to Satisfactory, without needing to hunt for hard drives on a map). There are now multiple "looping" recipes (the input items can be part of the output). Most notably, which recipes are available to you depends on where you are building - not only planetside vs in-orbit, but planetside vs in-orbit across all planets. The planets have different resources on them, and their orbits contain different ratios of resource-laden asteroids. Same goes for the routes between planets!
I was very afraid that the extension would feel like "more of the same, just longer and more tedious". That's the experience I've had with most overhaul mods I've tried, and notably why I never bothered paying Space Exploration (whose author ended up working with Wube on the Space Age extension). So far my experience has been the exact opposite. It really feels like every single new "thing" feeds back into the core gameplay by "rejuvenating" it in new ways.