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

Your friend highlights the gulf between differing persons' preferences in this hobby. It should be pretty obvious that as there are many different tastes in music, so also there are many different tastes in music reproduction for the home. There are sizable variances in how transducers produce sound, and the discerning audiophile will recognize that. To simply condemn certain types of speakers as no good is grossly ignorant ( I suspect your friend is actually stating his preferences strongly). You will want to find your optimum sound and then naturally will feel these genre of speakers are superior. But, be prepared as many will sense just the opposite. You will find that things such as imaging, tonality, coloration degree from cabinet contribution, etc. will become very important to you as well if you delve into the hobby deeper. 

I tend to enjoy speakers with less perceived cabinet contribution, and spend quite a bit of time with panel speakers for that reason. However, I can appreciate why many adore speakers with cabinet contribution. It's a classic case of YMMV. 

What Douglas said, + 1.