I did amateur boxing at university for several years and was quite good at that level, winning several amateur fights. When I left university I trained MMA and MT through my 20s, along with bjj and was quite serious in my training. I am late 30s now and still go to MT sparring for a bit of exercise in the medium sized town where I live. Thoughout that time, the vast majority of people that I have met in amateur boxing and MT did a little bit of training before starting low level bouts. At this point they usually continue on for a little bit then quit, drop back to club sparring level and don't compete, or go on to continue (low %). All of these people consider themselves to have boxing or MT experience, but most of that experience isn't worth an awful lot. Even guys who continue on and compete are a very mixed bag. This is mostly because decent training is quite hard to come by and a lot of coaches simply don't have a systematic strategic approach to the sport, focusing almost exclusively on basics. Good coaches are rare.
This means that many guys are either figuring something out for themselves with more or less success, or just taking a very basic approach. Taking a basic approach entails getting hit in the face because you have no intelligent coupling of movement to avoid getting hit and imposition of your game upon the opponent to make them do what you want. I would say that the average club amateur in either boxing or MT in the UK goes forward, is ok with taking a hit with tucked chin provided they can also land one, and lacks any more complex skill set. This means that in a fight they are waging a war of attrition against any opponent who also has the basics of how to punch and move covered, while against a skilled opponent they can become not much more than a human punchbag.
I had a good coach for amateur boxing at University who did teach a systematic approach to amateur boxing which relied on what he had worked out himself from his competition career, but since that time I have seen some awful teaching in boxing, MMA striking and MT. To me a low standard and lack of systematic approach seems more like the rule than the exception.
This problem is particularly obvious in MMA where you see many people under 1 year of pretty basic training having bought all of the gloves, wraps, gumshield and Thai shorts considering themselves to be "fighters". This is obviously nonsense, and beyond the basics such people people usually have no good understanding of how to achieve what they want to against a resisting opponent. Much less even than the average amateur boxer under 1 year.
My experience leads me to believe that the automatic defference often seen for "the boxer" is misplaced, because the majority of actual boxers don't understand much about boxing. Also I would say that assuming boxing is a single entity is not true. Different boxing coaches teach different boxing systems, while some bad coaches teach no system because they do not have a systematic understanding. Finally boxing systems are aimed at ring competition. Sometimes these systems align quite well with actual fighting, and sometimes they don't. There is no guarantee that "a boxer" is going to be an effective fighter. Boxing systems are too varied to make such blanket statements, and training experience too varied in quality to make any statement about any individual boxer. Good boxers usuing a boxing system suitable for real fighting can indeed be formidable opponents in a real fight. But many boxers are not.
VT in comparison is a particular systematised approach to fighting that emphasises apparent speed and safety. It takes account of the reality of actual fighting and makes some assumptions in the approach it takes. Because VT teaches a systematised approach to everyone, VT produces people who are from day one focused on imposing that approach on the fight. It is an approach that works in real fighting, unlike some styles of boxing, and it is a shocking/difficult/counter intuitive approach for the opponent. You may not like the approach that VT takes to real fighting, and you may disagree with the assumptions it makes, but as a rule I think it turns out people much more prepared for real fighting than the average boxing training.