So a few things and there, overall I love mesecraft, and it is what got me into minetest in general. I spent over a year playing it now, and has helped me go through a lot of health problems I was having. It is a good way to relax, and not think about anything.
A few suggestions/criticisms:
1. Torch burn out was cool at first, but became boring after a while.
It was cool at first, and made for some interesting game play while learning how to play, it forced me to learn the game and see what other blocks there was, but now that I learned it, it is kind of annoying. Yes, there are other light sources that do not burn out, the closest being the mese posts, but they have a hitbox/are kind of annoying to get around. It also makes the torch bomb/grenades feel kind of useless, because they will burn out before you really do anything in the area. There is also the tome of light, which is amazing, although it takes half of your mana, and takes a long time to recharge. (I love the magic system in mesecraft btw.) As for a suggestion, maybe there could be a end game torch that lasts forever, but it is more expensive?
2. After hitting -4000 or so, having no cave biomes is kind of boring, and makes mining mythril less interesting.
This one is not as big of a deal because I can just change it in the config, but that being said, I understand the reason why it was changed, most players do not go all the way down to -17000, although for players that do, going from -4000 to -17000 feels kind of pointless. The only reason to do so is to attempt to find mythril. I understand why mythril is so rare, and I am not asking to change that, its just there is nothing else there, and it just feels disappointing compared to the df caverns. I am not sure how to fix this one. But it goes into the next topic
3. Loot except for ship wrecks/magic chests is disappointing.
Loot in dungeons for example, you get a steel pickaxe, apple, maybe something else? All items that do not have a purpose once you dig past -4000 or so. At that point you most likely have full diamond gear, and many backups. At that point, the items are useless. Maybe the seeds would be useful, even more so if you havent found them yet, I understand that, but there is no reason for dungeon loot to exist at the point. Even more so in the nether. (More on that next) The dungeon loot in the nether is also kind of useless. Not long are dungeons harder to find in the nether, they do not give anything helpful at that time. (At least I havent seen any myself). I understand why surface level loot would not be all that good (for example, the sand temples, although the loot there is better than dungeon loot). I am not sure if it would be possible, but maybe add better dungeon loot the lower in the world you are? Also, I like the magic chests, those are kind of cool.
4. Nether is only a place for fast travel and maybe fighting mobs?
The nether doesn’t really serve that much of a purpose other than fast travel. Yes, you can find the portal blocks there, but once you have those, what other purpose does it serve? There is not much of a reason to go there, there is no ores there (yes you can make nether tools, but you just mine Nether Rack for that). The mobs are also harder, I do like that they are doom mobs, it makes it cool in that sense, but other than that, why go there? Dungeon loot does not give anything useful once you are already geared up. (Which if you are exploring the nether, you most likely are anyway)
5. Riding long rail tracks is not feasible due to dying of thirst/hunger
Once thing I love about mesecraft after coming from minecraft is you do not need to eat anywhere near as much as you do in minecraft. It makes long journeys easier, and it is significantly less obnoxious. Same with mob spawn frequency being low. I can easily just deal with a few mobs, and that is it. Although that being said, I am building a rail to the bottom of the world, which takes a long time to ride. I timed it at around 45 minutes to get to -10000. Although the problem is for long rail rides like that, you can not just leave the computer to do something else because you will die of thirst before you get there. I get not wanting people to be able to afk, but having long rail rides is not feasible because of it. (Although that might just be a me problem.) I am not sure how to exactly implement this, but maybe make it so you do not loose thirst when riding a rail? Not sure if that would even be possible though.
6. Lag that makes the game completely unplayable
I said this before on this forum, but certain abm’s perform extremely poorly. As in the game will refuse to function after going into some caves because CPU usage is at 100% for a single core. (That being the dynamic fluid mod) I do not mean lag as in a few seconds lag, I mean, the game takes 2-3 minutes to place a single block. My suggestion is to maybe add a config option for those features. The one problem I had (plasma in the underworld), had a config option that I was able to turn off. But the other 2 I had a huge problem with are: dynamic fluid, and gas seeps.
A few other things I dont have energy to get into right now but:
Villager Trades are kind of boring, not sure how to fix that though.
Moon/Mars is kind of boring (although I think you said that is a definite WIP, so I understand)
I love the magic system, but mana is sparse, maybe make an incentive to not die by making a way to increase your mana
I love the df caverns mods, they gave a wow factor, and what made me really get into mesecraft.
Just in general: Thank you so much for making mesecraft, like I said at the beginning, I have a lot of health problems, and mesecraft did a huge part in having me get through it all. Mesecraft is a lot of fun, I wish I had the energy to help contribute to it, but its difficult due to my medical issues.