Well I finally put 10-12 hours into SURVIVAL MODE over the last few nights. There's a nugget of fun in a more brutal, demanding NMS, but unfortunately the limitations of the inventory system, or possibly the punishment for movement, cut that fun off at the knees.
Survival mode makes resource management a much more important task. Which is fine, it's what you expect in a mode dedicated around "survival". Unfortunately, because life support drains so quickly (ESPECIALLY with movement), and because it can be so hit-or-miss whether you'll find the resources to replenish that life support, it actually severely limits exploration in the game. Your ship becomes your safe space, and the radius you can reasonably explore from there is a fairly limited without a full inventory of replenishment items (this is doubly so on extreme environment planets). NMS is all about exploration, but the limitations in Survival mode are so severe, going more than 1km from your ship is near suicide without an Exosuit already full of Thamium and Plutonium (or being on a planet just littered with those elements). Add on top of that the harsh limitation of one launch per 200 plutonium, and it makes most exploration a chore.
What would fix this? Well, no one thing would really make this better, but better stacking would certainly help a lot. The fact that we STILL cannot stack consumables on our person, when we can stack more "value" in the raw materials that make those consumables, just drives me insane. I'm not even looking for a lot of stacking (could be as low as 3 per stack in your exosuit), but crafting items should give you MORE value per slot, not less. Especially when there is no downside to using raw materials to accomplish the same function as consumable. I've also found it rare to be on a planet with plentiful Plutonium, but scarce in Thamium, making the transitive properties of the Power Gel of little consequence. In fact the only place where Thamium is typically scarce but Plutonium is plentiful is in caves, but caves are also usually devoid of Carbon, making that trade-off no better than just returning to the surface to hunt for Thamium.
"But wouldn't Exosuit consumable stacking make Survival mode easier?" you ask? In one way, sort of (it certainly reduces the tedium), but Survival should be more than just active resource management. NMS needs more environmental hazards. Even in survival, not enough of the creatures are aggressive, and on Aggressive Sentinel planets, Sentinels are just a constant, unavoidable annoyance that makes exploring those planets not really worth the trouble. Sure, large falls can kill you, but those are easily mitigated. There are still only a few plants that are dangerous, and caves are too safe, even if resources in them are scarce. No lava, no deadly gaseous clouds, no dangerous caves, too few dangerous plants or animals, too reliant on the unrelenting Sentinel army for "challenge", and too reliant on random resource placement for survival.
I hope they tweak it a bit and add more things to the world to improve Survival mode (and the inventory system) so it feels more like I'm surviving, and less like I'm just fighting an ever present, incessantly ticking clock.