While I do not use mods myself, I have noticed a few things:

1. Yes, there are mods for Valheim. However, because the game is still unfinished and the studio is yet to support modding, almost every time that it updates the mods will play catch up for a small time, be it hours, days or, worst cases, weeks.

2. As for vanilla game being unplayable, I would not go that far. Rather, you'll need a good head on your shoulders and a little bit of luck in order to get to the end. There is a grind, and some do not like it, while others do.

3. Returning to the mod question, I would personally wait at least a week or two before resorting to them as this will be the critical period for hotfixes that can make said mods obsolete until these are updated again. See point 1 as for why.

Now, regarding mods that may help out a single player, Benevolent above has given you the name for one that they find useful, others will probably follow.