There is more to ListenBrainz than generating recommendations, like the visualizations of listening history and the other exploration features, so I think you are being a bit unfair in your characterization of LB. Also, in my experience, the LB team listens to feedback and is willing to consider user suggestions. So it’s good that you share some of your ideas here.
That being said, I think the strength of the recommendation system is that it comes up with suggestions that do not follow from obvious links like shared band members. Personally, I treat the exploration lists as a complement to other means of discovery and am prepared to accept that not all of its suggestions are that great. And yes, I did manage to discover some new artists that way.
Finally, I don’t think everybody will experience the problem as severely as the OP. My recommendations aren’t all that bad. Surely, they contain the more established representatives from my corner of the musical universe (Aphex Twin, Massive Attack) but it is clearly geared towards my musical preferences. My impression is that most users will manage to get something useful out of those suggestions.