I can only give anecdotal evidence of a couple local to me flippers. One guy has probably five to ten each of nearly all main pieces of equipment in house at any one time. No room treatments, careless equipment placement, no AC upgrades. Last time I went over to purchase a piece, listened to what was his main system at time, always has at least two systems up and running, main system nearly $100k just in pre, amps, speakers, this with rather mid fi dac. Anyway, very blah sound, lack of resolving power. Upstairs system mid fi all the way although not mid fi price.
I could have put together the best pieces he had in house at time, take some care in what some call tweaks, made a very nice sounding system. This guy obviously doesn't care about sound quality, in fact he wanted mostly to speak about his obsession with audio shows and hob nobbing with audio manufacturers, designers. I see his items up for sale quite often, so still in flipping business. I don't see him giving advice on the forums I visit.
Another local to me I only had phone conversations with, invited me over a number of times, always made excuses not to go. This guy had limitless funds to spend on audio, but far more into cars, he always went on and on about his latest purchases of both, could tell from phone conversations he wasn't into music, all he listened to was heavy rock, and purchases were only signals of status. Boring, smug wealthy nitwit. Don't know if this one giving advice on forums.
So, based on these two, yes, they are clueless and I'd never trust their opinions about much of anything. On the other hand I've been in communication with former flippers who seem to have great knowledge of gear, tweaks, music. These guys I would trust.
In the end, I'd only trust former flippers, those who've discovered what they DON'T like, finally found what they like. While I never considered myself a flipper as I built systems slowly over many years adding new pieces now and then, I too found that discovering what I DIDN'T like let me understand what I do like. IMO, it takes this contextual knowledge to offer advice only to those who know the direction of their system building. The one asking for advice needs to understand their destination point, and the build has to reflect that. Without that understanding, one is likely to become flipper themselves.