My second suggestion is regarding exploration and endgame, but first let's have a look at my map after having finished the game (all bosses killed, big base max comfort with boar and wolf farm, explored mistlands and ashlands, etc…)
As you can see, I have explored very little of the entire map, and the main reason I explored that much was that it took me 10+ fully explored plains to find the location of Yagluth. One thing that struck me directly after finishing the game in its current state is how little of the map remains interesting, and by that I mean that there is little to no reason to keep exploring. Immediately after beating the last boss, my friend immediately said "Well, that was a great game" and I knew he would just stop playing entirely. He is a very objective-driven player, absolutely not into base building or playing just for the sake of playing, unlike me. I am sure that there are a lot of other players in this mindset as well.
Therefore, in this post I formulate a few ideas to provide incentives to keep exploring and provide some more endgame content and challenges to keep objective-driven players in the loop. I also take into account development time and try to look for solution applicable quickly so development efforts can be kept on adding more content in the main "storyline".
I believe that this question needs a tangible, practical answer to keep players (especially objective-driven players) in the loop. So let's explore possible reasons to keep exploring and playing.
Making gold worth farming
Currently with a single merchant and very few items useful for sale, there is little to no reason to keep looking for gold in crypts, underground dungeons in the Black Forests, by killing gobelins, etc… This could be solved with additional merchants selling quality of life or gear enhancement items. Here are a few ideas of items I would absolutely farm gold for are:
(1) An item that unlocks separate slots for gear, so your gear doesn't take your precious inventory slots
(2) A potion pouch to store all your potions and enable shortcuts to use them (these 2 have actually already been implemented by modders, see below)
(2) An item that expands your inventory size, e.g. 1 extra line
(3) Expensive magical gems adding either an elemental resistance to a piece of gear of an elemental damage to a weapon (I believe that a way to almost inifinitely improve your gear with gems would be ideal, I detail this idea further down)
(4) A key to a specific place on the map (that you need to discover) where good loot and challenge awaits you
There will be more ideas of items to be sold further down this post.
Rare elite mobs and/or bosses dropping valuable loot
I really like the normal mobs with their 1 and 2 stars variants. I could see the difficulty difference, however I could barely notice the loot difference, making those mobs more of an annoyance than something getting me hyped up for possible valuable loot.
One way to change this would be the addition of magical gems adding either an elemental resistance to a piece of gear of an elemental damage to a weapon.
Bosses should also drop loot valuable throughout the game, so there are reasons to go fight them again.
I really loved to see the utility piece of gear used to detect silver detecting burried treasures in other biomes.
Unfortunately for now, it's nearly useless since there's little use for gold. If we make gold worth having with additional merchants and interesting things to buy, then treasure hunting could be an interesting way to keep exploring, with better loot in more dangerous areas. Perhaps super-duper rare gear pieces or gear enhancing items?
There should also be something waiting at the endgame, after finishing the available content. Some sort of infinity game with increasing challenge. The first idea that came to my mind is to use the base raiding/events system.
Base defense challenges
Currently, I believe that base raiding events are severely underused and could easily provide near infinite replayability. For example, players could build a totem (a bit like the ward) that could require quite a few bars of all ores (to make it available only at endgame stage). This totem could then be used to trigger base raiding events of increasing difficulty with increasingly difficult challenges, and increasingly interesting rewards.
On construction of the totem, the players could start an event, first at difficulty 1, which starts the base raiding events they selected (Skeleton Surprise, The ground is shaking, You are being hunted, There's a smell of sulfur in the air, and additional ones). This could start as a first normal event, then on victory the level 2 would become available, which would spawn 2x or 3x as many mobs, then level 3 could spawn the normal wave but with 1 star mobs, then 2 or 2x more 1 star mobs, then spawn 2 star mobs, etc… Once all levels of mob invasions have been won, there could be boss invasions as well.
This type of challenge would force players to build bases specific for raid defense, while testing their combat skills, which should satisfy different types of players and be fun to do in cooperation.
However, for this to work and be worth doing, there should be some practical rewards to those events…
The path to God-like gear
Once we have provided a challenging infinity game as detailed before, we should give a reason to do it. The most straightforward answer could be those gear enhancing gems. Fragments of gems could be looted allowing +1 armor on gear, +1 attack on weapons, or +? of elemental damage/defense. The elemental gear could be worth farming for difficult levels of base raiding events (e.g. for "There's a smell of sulfur in the air" level 6 with 3x more 2 stars mobs), giving an inventive for players to create fire/ice/lightning resistance gear/weapons, surely providing a few dozen more hours of content easily. There could also be some cool looking elemental effects on this gear.
Wining an event could reward with fragments of gems, 10 fragments could be assembled/crafted into 1 gem giving of level 1, 10 level 1 gem could be crafted into a level 2 gem, and so on.
Hopefully some of these ideas will be useful.
In any case, dear developers, keep the good work going you are making a fantastic game!