Like with many aspects of trading, broker data seems to polarise people. I'd guess, confirmation bias also plays its part in both camps. More likely, the answer is somewhere in between, although to clarify, I'm talking about multi-week/month TFs here.
I pay the $1500/yr for my Pulse subscription because I only need a single decent trade idea/confirmation from the broker data, for the subscription to pay for itself many times over.
I'm also not naive enough to think that brokers don't trade through retail platforms and we all probably know some very, very wealthy individuals trading through ComSec, ANZ etc. Further, if BD was truly a massive advantage, it's inconceivable that it wouldn't be arbitraged away by the market, like all advantages are. I think the answer is that it can be a subtle edge, in the right scenario, when combined with other FA/TA strategies.
Made a post last year that covers a few scenarios where BD can give clues:
