My only gripe with SCA is the ungodly amount of farbiness. Sure there are some authentic groups/units, but it seems the vast majority are there for fun rather than for historic interpretation and presentation. You'll find everyone's got a strongly held opinion on the spectrum of authenticity.
It’s true that there’s a very wide range of historically accurate kits in the SCA. I believe it’s due to a combination of:
A) (Intentionally) loosely stated regulations
B) Duration of your membership (generally, longer = more accurate)
C) Time available for the hobby
D) Funds available for the hobby
E) What you personally want out of it (court follower, fighting, hanging out, education, classes, partying, etc.)
F) A 1,000 year time frame from 600 to 1600
F) All the above
With 30,000 members in any organization you’re going to get a wide range of interests and involvement. Heck, even the small Mercenary band I belong to has members up and down this range.
There are strong opinions held by many in regards to historical accuracy and which direction the SCA should go in the future. After two decades I’ve come to the conclusion that each individual must plot their own course. I take care of what I can with my limited means while remaining true to my greatest attraction to the SCA: Hitting people with rattan, repeatedly.