Preamps can be system dependent and personal preference do apply as well as musical tastes, what sounds mediocre in one system may actually sound very good in another. You might want to start by trying different interconnects and or tubes. If in the end all else fails you might need to try another pre. Some preamps are more accurate then musical, maybe that's the case here. Preamps are very difficult to get right for manufacturers.
Why some preamps does not play music? Cold?
I mean technically/electronically wise, why some preamps while been very revealing and very good in reproduction of frequencies and extensions, are at the same time not engaging musically and emotionally and even boring? Are there a solutions to fix that (except for changing preamp)?