Every time I try an active J or a J with non-single coils... this is how I feel too
I was so close to getting a MJ-5 but I just liked passive single coils better & went with a MIA J V Standard. I didn't like the MIA J Deluxe V for that same lack of character even in passive mode. (Theres a reason you see a TON of deluxe models up for sale)
I can't agree with the generalization. My main J-bass is a Warmoth creation with Lindy Fralin pickups and an Audere pre-amp. The Audere is so neutral and hi-fi that the great character of the Fralin pickups rings through. Lots of character. So it *can* be done, even if it doesn't happen often.