Well that's the least of the XMLs to edit; you'll also want to edit the groups so that certain zombies only appear in certain biomes, then do the same for loot. And sleepers.
If you did not consider Valheim a tower defense game that I think you did it wrong. Especially for boss fights, I found building preparation very important. For the weird wandering hoard things, defenses were also important. Way more so than in 7 days, when you can just clear a poi, make a few adjustments and be okay. Sure, valheim has its cheese (moats), but that's every game. Building in 7 days isn't even necessary. Hell a few players lay down some barb wire for horde nights and just jump back and forth over it killing.
If you want specific comparisons, then let's talk about the hand holding that the skill tree does. 7days guides you throughout. In order to get this, you must do that first. In order to do that, you must do these. Specifically, the skill/perk system.
Sure, you *could* ignore that entirely and play without leveling up the very specific paths, but then again you could turn your monitor off and play.
"Back in the good old days" when you learned skills from books and increased skill by doing, you weren't tied to a literal skill tree. It encouraged exploration and planning.
Right now you don't *ever* have to leave a decent sized town. Ever.
You touched on it with your explanation of valheim... One you have your character you could replay the game with that character, and I bet you'd still have fun. There would still be a challenge. A two star firling will still mess your day up.
Do that in 7 days and it'll be a yawn fest.
As an aside, it's very clear from the changes over the last few alphas that the direction tfp is going is thankfully biome based challenges. They've been establishing the foundation for that system for a while, and it shows.
Right now you can add lesser rad zones and give better loot in those zones with some small modding changes. Seems to me that's their eventual path.