A friend told me JBL DD67000 is actually very bad speaker, is it true?

Depends on the JBL! :)

I'm no fan of their current powered mini-monitors at all, but I haven't heard the high efficiency or high output types in a long time.  Worth checking out.

Also, a lot of boutique speakers get extra "imaging" but putting a dip in the response at 2.4 kHz or thereabouts. It's a trade off of timbral neutrality for it. 

For price though, I'd probably forego the consumer horns and see how much the pro studio monitors were running instead such as the M2.

No.  It is not true.

not true

Tidal, Kharma, YG, Magico, Vivid G1, Grande Focal and German Physik
speakers are all mediocre IMO.
So is JBL.

JBL’s newest designs are the best value in audio right now, nothing comes even close.