More teams now means more pitchers who wouldn't be in the majors when there are half as many teams like when Ruth played so while Ruth generally didn't face as many different pitchers in a game, the pitchers he did face were probably generally better than the average pitcher today even if they weren't all throwing 100 back then.
It really is tough to compare raw numbers from different eras with so many variables. That's what the advanced stats try to adjust for. One example.
OPS+
Ruth 206
Ohtani 148
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