You can't change one part of a system and expect the old bits to just "work". Heating and upgrading became more tedious to combat the free elevators, which essentially removed the limited playability per day of the game (heck, you've already identified this). If the old heating system was still in place, upgrading would be far more straight-forward, and you'd finish the game earlier, which is likely why it was changed.
Quite frankly, I don't care if that's true or false
That's a horrible statement. If the heating is exactly the same as the old system, you're complaining about that being too slow too. If so, the issue looks like the level-to-level bit. As in, the use of fire crystals, yet you repeatedly say that's not the issue. What is it then?
I've been playing since day 1 of steam, so you can expect long-term players to get more bored than more recent vanguards.
That's... kinda obvious..
If you've been playing longer and completed more in the game, you're bound to get bored of it earlier than someone that's only recently hit end-game.
All in all, you seem to be contradicting yourself. You want the game to give you more to do, but you don't want to take very long doing it.
Even in your last post, you say the slow heating is boring you to death, but then you go on to say the point of the game isn't heating.
@Cradarc
"the heat gained per mission was not modified."
Quite frankly, I don't care if that's true or false, because I remember when I first got my Vog Cub Coat, it was thew only item I needed heating (this was before the forge), and in two firestorm runs, I got it up to Level 9. The only thing I need to heat right now is my Master Blaster, and if I do two runs then I will most likely just bump it up to nearly a full level.
"Can you clarify your position on this issue? It's kind of important if we are to discuss it constructively."
I don't mind farming crystals, but I do mind trying to gain heat. The only reason why I'm farming FSC right now is for heat, as it's the "quickest" way. I'm just not motivated to play the game anymore.
"Are you implying that those things are not possible while heating?"
Well, they are possible, but slow heating is boring me to death. That's why I haven't played the game in about 5 days. I go online, but then I just go offline straight after. I don't have any motivation or goals in the game. I don't really care for guilds, upgrading weapons is extremely tedious, sure, we getting more missions and all, but right now I'm getting tired of this game. I've been playing since day 1 of steam, so you can expect long-term players to get more bored than more recent vanguards.
"My original point is that the heating process IS the game."
I thought it was to party up, play arcade and enjoy the game.
@Ellthan-Cosmolion
No, I haven't seen that movie.
@Duskfinder
"Why not just make the forge available at the beginning of levels or at the end (when it shows the heat meter)"
Because then there's really no point in doing arcade then. You'd have everything you'd ever need in boss runs (except alchemy machines).