A system that does not engage in some sort of full contact environment is also suspect of being a “McDojo”. Any system of martial worth engages in some sort of resistant training or sparring. Schools that often lack credibility do not engage in such activities. There are many reasons why they do not. The usual answer is that their techniques are too “deadly” for sparring. The reality is that if full resisting partners were introduced most of the techniques these schools taught would be ineffective in subduing, injuring or even killing the assailant. Therefore to protect themselves from this reality the full resisting training is eliminated.
However, if you are looking for a more realistic or self defense oriented school a continuous full contact sparring that allows contact to most of the body (lower and upper extremities) is more suited toward your needs.
There are currently internet organizations that dedicate their time to researching and exposing schools in which conduct themselves in a less than ethical manner. Most of these organizations conduct themselves in what is called “forums” whereby martial artists from various styles and ranks discuss elements that are commonly found in more legitimate organizations and systems. During these online discussions many schools suspected of being fraudulent or adhering to a “McDojo” practice are uncovered and/or exposed. These forums are usually discovered during your internet research if the school has had a turbulent history in the views of different organizations.
While I certainly agree to much of what you said here, I will touch on a couple of points. First of all there is no such thing as a fully resisting opponent in training as they are not actively trying to cripple you, because it is training not a street fight. Secondly fully resisting is not always the best way to go, there are somethings that if you resist too much you will wind up getting seriously injured because the person applying it will have to apply full force (a wristlock for example).
Thirdly I often hear this "too deadly for sparring/competition" line from people who do combat sports when describing arts that do not compete and only train for self defence yet many techniques are removed from full contact (no such thing as that either) competitions for "the safety of the competitors". If these techniques are not too dangerous for competition then why take them out? Striking to the throat, neck or groin or breaking the knee with a low side kick is certainly not safe. Fourthly full contact sparring is not the be all and end all of training. For a start only certain targets are allowed and often these are parts of the body that can be conditioned to absorb blows, such as the stomach. You then add gloves, body armor and head gear and it instills a false sense of security because you think you know what its like to get hit. Exactly how do you prepare yourself to be hit in the throat, neck, groin, eyes, solar plexus, knee etc, you can't. Full contact sparring is not a Litmus test it is just a method of training. Full contact sparring is not the only way to add realism and in many ways it takes some of the realism away.
Fifthly the height of the techniques and the presence of flying and spinning kicks have no bearing on the credibility of the school or art unless every kick is aimed at people who are 7 feet tall. MMA is often see as the only legit art by the unenlightened and they do all 3 of those.
Sixthly internet forums can be a very unreliable way to gain information on the credibility of an art. You get people with no serious martial arts training offering their uninformed opinions, MMA fanboys who think that any art that does not appear in the UFC is a useless joke just because they saw some mid level TMA guy loose one fight to a grappler (never mind all the fights they won), people from Mc'Dojos/Mc'Dojangs go on forums too, people who spent 5 minutes watching a class and decided the whole art was crap because they didn't have the slightest clue what they were looking at, not every art is discussed on forums or makes videos, sour grapes from disgruntled former students, students who sucked at the first martial art they tried who didn't put in much effort when they were there and got beaten up saying the art was useless, instructors buttering up their own styles and people with bias towards a certain martial arts type etc.
Bottom line is to find a legitimate school do a little research to see if it is something you might like to do and go check out a class. If the instructor seems to know what he is doing and you think you can learn what you need to from them then give it a go. Any school worth a damn will offer one or two free lessons. Avoid contracts because it may take a while for you to discover if the art is any good or not or if you want to train to train there for a long time.