I'm not sure what your original intended scope was for Grimoire of Worlds, but looking at this, I think it's safe to say that your scope has gotten completely, wildly, profoundly out of control.
I think more simply, why would anyone want to visit billions and billions of planets if they're all basically the same, save for maybe slightly stronger monsters or something? I get that they're randomly generated so it's not a big deal to make 'em, but still.
Actually my scope has gone down profoundly. Up until recently there was 10000000002 worlds, now it generates just over 8200 worlds, mainly because I cant fit more in a galaxies image. I considered making multiple galaxies, I even wrote all the code for it, 10000 galaxies each with between 6000 and 8000 stars and each star with between 1 and 7 planets but we can both agree that over nine hundred thousand worlds would be to much. so I took out the multiple planets per system and left it with just the one galaxy. There are 14 different world types so far but I may add more.
Also Ores, Herbs, Wood ect are procedurally generated according to world difficulty so the more you explore you will keep finding new better stuff for making better potions/equipment.
As for who would want to explore that many worlds, Elite, Elite Dangerous, No Mans Sky, Cubeworld, Minecraft. They all have a massive amount of exploration(beyond what is possible to explore in a human lifetime, well maybe not the original Elite) and they also don't have enough variety in biome/world generation to make all those worlds/areas fun to explore. but I know what you mean, there is something that feels defeating about knowing you will never be able to explore everything the game has to offer. But also the truth is you don't have to explore all the worlds. Its more of a play how you want to play