I've been in this hobby nearly 10 years now. Not as long as others but long enough. I don't disagree with you that following those trends can minimize risk. It certainly can. No argument there, at least when it comes to "party friendly". With party girls specifically, I get that the main worries are erratic behaviour as well as following up on agreed services and the quality of those services. Personally, I have never experienced erratic behaviour with party girls but I have experienced changes in services and poor quality services. For me, as long as they can act right and deliver good quality, idrc if they party or not.
As for the ethnical part, I can't attest to that as it does not affect me. All I can attest to is that there are many well reviewed, reputable providers who do have ethnic preferences in the clients they see. Some will see black gents and not middle eastern/Indian. Some will see both of those but no Asian gents. Also, there are plenty of black female providers who also don't see black gents, so like that's clearly not a racial discrimination (or at least most likely). My point is mainly that these ladies can see who they want and what clients they prefer to see generally can't be used to indicate quality of service. Hell, I'm sure there are even incredibly high-end, upscale providers, higher than Amber, I'm talking in the 1k-10k/hour range (who from my understanding are usually legitimate pornstars that also escort on the side), who are party girls or have ethnic & age preferences who are incredibly well reviewed, reputable providers who see the most elite clients. It literally means nothing other than for whatever reason they don't want to see certain clients.
Like, if you do fall under the ethnicity or even the age of client who they would prefer not to see and you show up anyway by either lying or avoiding telling them, you're likely going to get turned away or they will reluctantly see you and you will have a bad time. However, with that said if you are polite and respectful when communicating there is a chance they may be willing to make an exception. When I first started this hobby in my early 20s, I fell under some providers age restriction. Be it "no gents under 30 or 25" or "25+ or 30+ gents only" or whatever. But because of how polite and respectful I was, they usually made exceptions for me and I had a good time. I have also seen ads for ladies who only want to see older gents, typically 40+, 50+, 60+. I've reached out and have been turned away every time. Oh well

I was even turned away by Katrina (sexy blonde lapdance and bbj gal most of you are familiar with) when she first started a few years ago because her age restriction was 28+ only or 30+ only. She does see all gents though, I think?
I've even been turned away by Candi, after the last time I saw her. After my last session with her, she said she would not welcome me in the future because I couldn't cum from a BJ in 10 minutes or less. (I can do a normal bng session, 15-20 as per my past bng reviews with Jenesis, Bambeigh, etc.). I asked about her quicky fs when she offers it because I know I can cum from an fs quicky in 15 min or less especially with someone as attractive as her and she still said no. I've never been turned away for this reason, that was a first. But hey, she prefers to see gents who can finish in a shorter than normal time. That's her preference, nothing against her at all. She's a lovely woman. Sucks that I can never experience fs with her because I would love to but again oh well, it is what it is.
I do recognize that for many it can be frustrating to see all the ads with party friendly in it or with the same ethnic or age restrictions. I do 100% understand and empathize, despite generally being unaffected by them. The only thing as clients you can really do is just find and see the providers who welcome all gents or on the case of party friendly, those who don't party aka "D&D free". That's really all there is to it.
However, I hope I've indicated that I do see the problem from both sides. I get it. In a perfect world, in this hobby, if everyone could see everyone that would obviously be great and ideal. I'd love to see that. Unfortunately, we live in a world where the bad apples spoil the whole orchard. This is indicated by both sides. Specifically, those of you who choose not to see party girls from your bad experiences with them. You write all of them off despite not all of them being bad. The same is with them and the clients they don't want to see. They've likely had bad experiences with those clients in the past and don't wish to see them anymore. It is what it is.