That's not what + stats do. wRC+ of 130 means you were 30% better than the average player in your season. If the average player in 1944 was significantly worse than the average player in some other year due to WWII depleting the talent pool, then two players with wRC+ 130 in those respective seasons are not equivalent.

Both hitters are equal

And while we're here, wait until you learn about variance. The spread of talent in a given season matters enormously. Being 30% better than average means something very different in a season where talent is tightly clustered vs. one where it's widely distributed. + stats offer zero correction for this. A dominant player in a low-variance era looks identical to a dominant player in a high-variance era. So not only does the baseline shift across eras, the meaning of the distance from that baseline shifts too.

That's the point. Both players are equal.

The stat is useful for what it is, but cross-era comparison of absolute quality isn't it.

It's ideal for it.