I usually have no problem telling Seiyuu apart or in recognizing a voice in an anime, or at least I've gotten a lot better about it. Tomino's words strike me as more evident of him just disliking how anime, and characters in general, are portrayed in the modern era and how he believes VA's are suffering for it. While I can understand disliking the current trend of anime, I think there's tons of distinctive voices within the industry and even if you dislike those voices, there are plenty of good and interesting performances to be found in any season of an anime.That's just my opinion though
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That said, I admit I sometimes have a hard time telling Ayana Taketatsu and Ayane Sakura apart, especially when it came to the role of Suzuka Dairenji for the latter. And Ami Koshimizu can sometimes sound like Mai Nakahara depending on the voice she's using