Just the opposite for me though I don't listen to much Rap, House or current top 40 type stuff though somethings do catch my ear. I do own some of each that have caught my ear and like you own lots of old rock along with things like Radiohead, Jack White etc. etc. When I evaluate, I always make sure to use some acoustic jazz and classical recordings that I have 1st hand knowledge of and thought the DX90 was more true to them. There a specific cut (First Song) with Laurence Hobgood, Kurt Elling and Charlie Haden That's sounds good on everything yet can tell you a lot. Charlie used a Vuillaume bass with a uniquely full sound that's difficult to capture both in recording and playback. It's a good test for bass character on anything, a well tuned and recorded Steinway is also telling and I have heard Kurt without a mic.
None of these DAPs are perfect, far from it but I appreciate what iBasso have accomplished for the price and package. I don't think it's necessarily the best I've heard but the things I've heard that I feel are competitive all cost over twice as much. For me the X5 obviously isn't one of those but for others it is. In an imperfect DAP world, I find the DX90 a nice place to hang my hat for a while if not longer. I honestly prefer a couple of my Hisound players to the X5 even if they have a bit of an unwarm sound, some thermal noise and are limited to 24/48.