Was that the only thing wrong with it? The 90s was definitely before my time but I was under the impression reading about it that there were also fundamental flaws with DES which lead to the competition which ultimately produced AES.

Yes, that was what was wrong with DES. I mean, it also had an 8-byte block size, which turns out to be inadequate as well, but that's true of IDEA and Blowfish as well.