I feel as though endgame grinding is mostly fine except for a few key points-
1.) It's very hard to get into, because the game only gives you enough rads to heat maybe half a set at most. I've addressed that here-
https://forums.spiralknights.com/en/node/123625
2.) There aren't very many areas to grind in. We have all of Dreams and Nightmares and Firestorm Citadel I've addressed that here-
https://forums.spiralknights.com/en/node/112706
Radically reforming the crafting system is a fun thought experiment for the suggestions forum, but is costly and risky in practice, as you risk losing players who have put in the work already, and muddling with the system tends to produce unnecessary complexity.
I think the most obvious solution is to release the next set of missions, move the danger missions and others I've listed down a bit, and have these new areas be difficult + fun radiant fire crystal farms. I also think that giving the player enough crystals from the get go to heat a set and a half would help them tremendously with breaking into these difficult areas.
But, if you want sweeping reform, might I suggest losing heat instead of fire crystals when you fail a forge?
https://forums.spiralknights.com/en/node/119992
Solution #3: Allow radiants to crafted from shinings, ect.
There really isn't make much sense that Crystals can be broken down into its lesser form but not the other way around. I would say 10 shining -> 3 Rads is a reasonable conversion rate. This would allow new 5* players to actually be able to craft their gears through arcade and give the leftover 3* / 4* crystals some use.
Solution #4: Increase crystals quantity per CE purchase in the supply depot
I am no economist but, demanding 700 CE for 50 rads at the supply depot is ridiculous. 700 CE is what you would have to pay at minimum to craft one 5* gear back in mist era. So the fact that 50 rads wouldn't even get you 1/4 of the way from heat lvl 9 to 10 on a 5* gear is an insult to players' intelligence (whales or otherwise). It should be at least 300 rads for 700 CE and even then it is a rip off. But this is GH we are talking about here, the same people who had the GALL to sell gatecrasher helmet at 3.8k CE.
If you want to do P2W, at least do it right GH.