Which is why you need a grounding on what to look for.
But what should that grounding be? It shouldn't be avoid such and such style because if that is the case people could end up missing out on great training.
I have been told everything I have done in martial arts is **** by at least a few folks. That is how it is, everyone has their opinion whether or not they are experienced. If I listened to every person to be honest I wouldn't be doing anything, because everything has some people who will call it crap.
For example. When I did American Kenpo Karate it was " that stuff is fake and doesn't work, do boxing." Even on a deeper level it was "don't learn American Kenpo from that guy, that guy is fake and charges too much "
Right because the competitions we won were all fake (rolls eyes). Then it went to "don't do martial arts, all that Chinese crap us ********. Just get a gun because nothing beats that." After that it was " Your sifu is a fake and his sifu was a fraud with a made up lineage and overall fake history."
I never cared about this because all of these opinions are exactly that, opinions that anyone can have whether or not they have any knowledge. I give people benefit of the doubt because in the end the opinion that matters the most is my own.
Sadly there is a risk involved here. The risk of dedicating yourself to a bad outlet of training. Sadly that is a reality many of us have to face because there is always that chance. Even if the instructor is good or phoneomenal, maybe his or her methods won't work for you? There are many things that can happen here that are just out of our hands and are in general going to be unknown until you actually give it a chance.
I myself have been to a mcdojo before in middle school. I was lucky to know it was bs before hand though because I had asked the more senior students if they ever sparred with each other, they literally said to me "what is sparring?" All we and they ever did were hit pads and do moves on the air.
That was my first and only experience with shorin ryu karate, now there are two things I could have done here. I could have gone around and told everyone I know "Shorin Ryu is fake and cheesy" or even worse "karate is fake and cheesy" purely based on my one experience. That would be nothing short of ignorance, now if I said hey that particular shorin ryu karate dojo is not that great because ect ect. That would be much more appropriate.
I think the grounding you are talking about should be the following instead of just avoiding entire fighting arts all together.
1. Know what you want out of the martial art training.
Example: become a pro fighter, simply get in better shape, self defense training. Simply something to do.
2. Look at it more as learning techniques rather than learning a style.
3. Ask yourself will their training regiment be able to help me get what I want out of it?
For me I want to go into karate tournaments and get far there. I don't particularly like mma simply because the attitudes and stigma that surrounds it, that is by no mean meant to offend you or anyone but that is my personal oppionion about it.
More importantly I don't feel comfortable in nothing but board shorts and feel much cooler in a gi. Maybe someday I will go into more mma stuff but for now I am more interested in the more stand up scene. So those are my goals and that is why I am happy where I am at.
It really takes a lot of looking deep down and understanding what it is you exactly want, and nobody can do that except for the individual.