With two major biomes to go and whatever else it needs before 1.0, two years might be a decent ball park guess.

Go ahead and jump in now if you want. The game is fully playable even if it's not yet complete. There is a clear progression, but not a fully fleshed out story. I haven't played Elden Ring so I can't compare it there, but Valheim is a game that is said to be "too easy" by cautious players and "too hard" by fools who rush in. It will punish your mistakes, and sometimes teaches things the hard way, but the vast majority of mistakes are preventable.

I consider myself to be a B grade solo player and I do fine. (Never got the hang of parry timing, and resort to cheese at times, but it still works.)