Ever since the big update on revives/heating/crafting, I've found the game less fun. My reasons are a bit different than yours though. (I also am a VERY endgame player.)

I no longer find the levels challenging. With 1 free revive per level I go all "kamikaze". I hardly ever die once per floor, never mind twice. When I do die, it is not because it is challenging, it is because I get impatient with the "puzzles" (spike traps, status traps, shankles, etc.). I literally just run right through them. Back when we could use health to revive teammates I had an incentive to stay alive. Every health bar mattered and I tried to not take any damage. Now when need I revive someone I need to fork over 20CE so they don't have to pay 50CE. They should keep the old revive cost system, but start it at 20 CE. (1st revive=20CE, 2nd revive=40CE, 3rd revive=80CE, etc.) I don't think health splitting should be brought back because OOO needs to make money somewhere.

Heating system is only broken for 5* weapons IMO. I see a lot people with a lot of 5* gear that isn't heated all the way through and I feel bad for them. All of my gear that I use is heated to level 10. I don't have anything that I really need to heat to level 10, but when I do I despise getting radiants for them. They could easily fix this problem by allowing radiants to start dropping at D21. Shinings could still drop throughout T3, but people NEED more radiants This would also give people an incentive to run arcade instead of spamming FSC and allow them to heat their gear a little bit faster. I doubt anybody pays 700CE for 50 radiants anyways. Maybe I'm wrong though.

I think the crafting system was an improvement as it encourages people to hunt for orbs and actually play the game to get good gear. Back in the day, the only way to get good gear was to pay for it. Now you can actually craft things for almost free. I think OOO still makes a lot of money from selling orbs. I know I buy all my orbs except for eternals. The cost for alchemy is still the same, so I don't see it being a bad change.

The elevator change was necessary to make Spiral Knights truly F2P, and I understand that OOO has to make money somewhere. I think the game is better off the way it is now, but I found it more enjoyable before all of these changes. I thing the only massive problem is the revive system now. However if you bring back the old system, you bring back elevator passes. That makes Spiral Knights P2P. I am fine with the way the game is now, but must admit I did like it better before. I can't really understand this game from a new players POV though. This is just my opinion after playing the game for a few years. I think it is almost like an entirely different game for newer players compared to when I started. Sadly I don't think newer players post on the forums as much as older plays, but I would love to hear their opinions.

yay, first long response in a while.

orbs aren't overpriced, they cost the same as old crafting costs, and they can be found in the clockworks. if you refer to the times in which crafting costed half of what it is now, I think you can blame mission grinding for that.

the forge was put in place to balance out free elevators, and it's effectively better for new players and way, way worse for endgame players because radiant drought (have to test this out due to rumors, but let's just say they're rumors for now). before, a newbie had 100 mist to play the game and then it was stopped by a 7kcr wall for 100ce, wall that you could go around by the time you were 3*, but it would have taken a while. now there are free elevators and fire crystals are less required and less rare at lower depths than they are in T3.

sparks cost 200ce per 10 pieces, and can be found in the clockworks. here the matter is a bit iffy. if you want to gain ce over the old revive system you have to die 5 times and revive (counting the ER). maybe with the old spark drops this could have worked, right now there are guys like me that have 12 sparks and don't want to waste them.
health sharing could drag down a team because of one member, and induced a whole lot of alt dragging. OOO solution was a bit radical but hey, works for me.

tackle, challenge is something that OOO has slowly pumped out of the game, with the exception of SLs, and that's basically because they don't want to scare newbies out. pretty much all end-game players want something more challenging without having to spend 1.8kce.

Unfortunately it probably won't happen because if it changes, the new people who are used to the new will complain and there would be a huge fight between the vets and the noobs. Then OOO will have to pick sides. If one side loses they get upset and leave and vise versa. It's time to just either except it the way it is or just stop playing and move on to something else.