Look at his baseball savant page, which tracks a number of advanced metrics. The only guy in all of baseball who has a page that looks like Ohtani is Judge. And Judge is also having a historically great season.

Ohtani is overly penalized by the DH spot in terms of WAR/fWAR. It's hard to find other metrics when it comes to hitting that knock him off his greatness perch.

If we look at Judge as an example of the flaw with WAR, we can take away a few things. In terms of defensive performance, Aaron Judge has played more games at CF than any other position this year (he has also played 37 games at DH). In terms of players who have played in at least 100 innings at CF, Judge ranks 68th out of 71. In other words, it's not good. But he gets a lot of credit for simply playing the field, because it opens up the DH to another quality player. But he is a net negative for the Yankees in terms of his defensive performance.

In other words, it's ok to look at Ohtani's offensive performance and compare those numbers to everyone else without hammering him too hard on lack of defense. Judge doesn't get hammered nearly as hard when he is a poor defensive player and still plays a significant number of games at DH. If Ohtani comes back and pitches, that suddenly takes his value to astronomical levels. But if we just look at his hitting, we can certainly appreciate a historic season without using a single stat to tarnish it.