First I'd like to say that I think it's a great game and I do enjoy it.
HOWEVER. The leveling is so unnecessarily grindy. Yes, unnecessarily. To get to a lvl 100 fishing you would need to reel in the line continuously for over 30 hours irl, and that is excluding all the downtime of raid events, mobs attacking you, actually casting the line etc. That is runescape level grind in a game that does not have use for special fish except for single one (anglerfish) and in which the gameplay of fishing boils down to "Ya got enough stamina, son?"
Obviously, fishing is a very much an optional skill in the game, but its one of the worst offenders so thats why I brought it up. Another bad for the grind is blood magic. On paper the skellets leveling you every time they hit something sound alright, but trying to level it you quickly realize that skellets not having any AI improvements to regular skeletons renders them mostly, if not completely, useless. I just summoned bonemass to try to get my blood magic level up, only to realize that melee skellets cannot hit bonemass at all due to some weird routing reason — they just go up to it and stand there getting killed. The hp cost of 40% is much too steep for a summon that is not that strong, cannot route anywhere and if it gets to the enemy just stands there idling.
Speaking of magic, in order to use it anywhere near effectively you have to consume ATLEAST 2 eitr foods, which means you only have 1 slot for either stamina or health, and in mistlands you really need stamina to just traverse the terrain, but you just can't go without the extra hp due to spellweave losing a hefty 50 p of armor from carapace and due to that you need to use the blood magic barriers constantly, and to do that you need the hp. There not being any type of jerky in mistlands is such a kick in the shins for anyone who wants to use magic.
All that said,the leveling would still be somewhat justified if you didn't lose an unscaled 5% everytime you died. If you like to organically explore and finding stuff out for yourself without looking up a strategy guide BEFORE moving onto a new biome, you're going to die a whole bunch when you do so. This means skills that you don't constantly use (fishing, riding etc) damn near reset when switching biomes. So in that sense, the game is actually punishing you for exploring.
Also gaining completely new weapon types at the (current) endgame biome with a leveling system that gives exp with connecting hits seems just counterproductive. Like yeah I could start using this cool broadsword now, but I'm literally lvl 60 in maces.
My own suggestion to improve it would be either to remove the death penalty (lol), or rework the leveling system to give more exp for more dificult enemies.
//Edit;
Just to hammer on how grindy the leveling is, our host who plays like a pussy has a much safer playstyle than I do is lvl 80 something in running. That is a skill you use constantly while playing. We've played over 100 hours of our current game.
Source: https://www.reddit.com/r/valheim/comments/11t5iji/my_gripes_with_the_leveling_system/