I used to play on 1.12 modded but now i'm on 1.19/1.20 stuff, I know there's a bit of a mod gap with a lot of the big classic mods stuck on older versions and they might never update, so there's a whole new ecosystem of mods for recent versions. I have played Create: Above and Beyond as well a tried a few other create packs, they're pretty fun but I didn't go far enough into them to know if they're expert enough, but they didn't feel grindy for the sake of grind to me (especially if you've played 1.12 modpacks like gregtech and such, none of the recent modpacks ever come close to the level of grind you'd have in old modpacks).

There's a new one that looks really cool called Create: Arcane Engineering, which looks to be pretty expert, all about combining tech and magic. Not necessarily grindy, but from the start a lot of basic steps are much harder to make and you are basically required to automate things, which Create is really made for. There's some things that feel kinda dumb/annoying in how hard they are to get and automate tho so i'm not sure. It has a big quest book with a bunch of parallels branches (often separated magic and tech that end up joining together, you have to use both fully at some point to progress), and a bunch of stuff that seems more tailored for servers where players are encouraged to specialize on things and trade.

Edit : I've also heard good things about Create: Astral for space exploration. There's a lot of create modpacks, it's basically the core mod of any tech modpack now. There's some big mods on the Forge side that don't exist on Fabric or don't have alternatives yet, it depends what kind of mods you prefer.