I've completed all the rank missions, heated my 5* gear to level 10, got my sprite to level 100, done Operation Crimson Hammer, done a shadow lair, and have all my desired gear. Now what do I do? I still find the game fun, but I can't find anything to do. In any other game I'd just start a new save, but getting to the end in SK is such an investment that is just isn't worth it. The endgame feels way too lacking and anticlimactic for how much work you have to put in to get to it. I've just been doing FSC like once or twice a day while I rack up crowns that I don't know how to spend.
Now what?
How broad is your "desired gear"? Have you tried playing as a damage bomber? As a support bomber?
I don't know you, so I'm not saying that you haven't. I'm just saying that this game plays really differently, depending on your weapon mix. And you should try all of the mixes, if you haven't. :)
The game also feels really different playing solo vs. in a party. Your party members really alter the monsters' behavior.
As far as your unused crowns go, you can spend them at Punch, or you can save up for a Mixmaster or Orbitgun? Or for Margrel fights? You haven't mentioned Margrel.
You haven't mentioned danger missions. Heart of Ice is pretty challenging for most players. Some of the special event missions (Grinchlin Mountain) can be tricky.
If I had to hazard a guess, you likely have mostly meta gear and one battle sprite.
Try going for a different sprite! Its good to have one of each, as each is useful in its own right, in specific missions etc.
Try a new fighting style. Level up some alchemers so you can alchemer switch in graveyards!
Maybe try learning vortex+sudaruska techniques for solo! Or mess around with a catalyzer in jelly king.
Ultimately the game doesnt have a super engaging endgame so most of us out here try and make our own fun. When we get good enough to do vana in our sleep, we shake it up and make it more fun.
Theres also nothing wrong with just taking a break and waiting for the itch to come back.
Funnily enough, a popular thread by Reydann was posted beneath yours earlier discussing this very problem.
Luckily enough, a dev replied and confirmed that they'll be working on incentivising players to engage with all of the game's avenues after they modernize the game (their current focus).
I recommend gathering friends or guildmates and running a super chill Arcade session for the hell of it. No speedrunning, no loot focus, just vibes and an active background to a chat or hangout.
Not much of a solution or a thing to do until then but can be enjoyable if you're with the right people and you'll still be getting a smattering of loot regardless. Playing something else while keeping a close eye on the game until it updates also can't hurt, whatever will pass the time for you.
Until then!