Where to start? It's possible that they are improving, but I still think there are better ones - like Phoenix Rising!
AfME were founded by what I call the psychoquack mob, I believe - the particular group of psychiatrists/psychologists who muscled in on ME/CFS decades ago and claimed it as basically a psychosomatic illness (they have since invented several other words for 'psychosomatic', presumably to confuse people). Thus the psychoquacks are responsible for the fact that there is almost no proper treatment available in the UK for the illness, and that patients are instead sent for psychologically-based treatments that are more likely to harm them.
AfME still often seem to promote psychoquackery, and when I was still using their website they had no platform for scientifically-literate people unless they were also health professionals - which in many cases in the UK is in fact a contradiction in terms! For example, I commented on a piece of research they had in their research section, but never received a reply - turned out no one was monitoring the section. Maybe they still aren't.
Up until recently they were coming up with what appeared to me to be phony new 'initiatives', like 'Time for Action' which everyone was being urged to put their names to, and get their friends and families to do the same. When I pressed them to tell me what exactly it was about, they listed a load of activities that Action for M.E. was already supposedly committed to doing.
I think the ME Association is better, as are a few others in the UK. But before thinking of joining anything, do a search on Phoenix Rising. It is a mine of information!