The Richard Harris Cromwell film had more fighting and more "hair" on it (guts) Fairfax was not in the story. The problem may be the "funny clothes" issue which makes costumers modernize period clothing for contemporary audiences. ECW wigs, effeminate lace colars and cuffs, facial hair, heavy and high waisted men's clothing, and big pants might be seen as a problem. Tighter pants were worn in the recent 3 Musketeers for instance than what was worn. They mentioned THAT in the movie comentary.
Funny that correct clothing didn't hurt the Richard Lester 3 Musketeers 1970s verions.