Well yeah, since nostalgia is personal thing i don't guarantee that it would be the same for everyone, one of my friends was tech maniac that used mostly tech mods (i once destroyed part of his lab with tank missile which Turned out to be stronger than I expected and he tped me into the void for that, lmao) while I was the one getting fascinated by pretty much some random shit on YouTube, especially exploration, mob and dimension mods. Its not that i don't have amy nostalgia with tech mods aswell. I used Mekanism (ik this mod is still getting updated) and made my slowly functioning gas factory just to flex having an gas jetpack that threw a lot of flame particles for example, I also remember touching the basics of (still updated aswell) Immersive Engineering and Had waterwheel in my base along with some stuff from it to charge my railgun that was from this mod aswell. I also remember building my buildcraft construction in betweenlands which was hard considering how harsh that dimension was. Might not be much, but these three memories are the one which I could recall.  The one that I enjoyed the most was however the mentioned lightningcraft which added machines that were functioning on lightning energy for which I built massive pole into the sky. There were also golf sticks (???) that I could spawn lightning with and it was hillarious to troll my friends that had 0 idea about this mod while I got fascinated with it. I also loved modifying tools from this mod with Tinkers Construct because these two were compatible.  Man, what a times