Panellists and audience members alike agreed that far more heterogeneity of clothing was called for, with costume designers needing to think harder about dressing characters in clothing appropriate to their social status, and using more homespun cotton and wool, perhaps with the occasional quilted jacket to distinguish Our Heroes from mass of minor (and lower status) characters surrounding them, not to mention the flowing robes that far more of them ought to wear when not off adventuring or fighting.
Of course it's not just the heroes. Female characters are all attired in remarkably similar corsets, regardless of status, generally decorated with lace even when such adornments would be beyond the means of the average lower class heroine in the street. And it's very rare that characters (female or male) in any historical drama are depicted wearing make-up in keeping with the era. Yes, Georgian-era dandies did wear at least as much make-up as the women they were wooing!
The panel were, however, keen to point out that we can't entirely blame costume designers for these deviations from historical accuracy. Audiences are assumed by all those involved in the production of historical series to come with certain expectations and assumptions; to show male characters wearing high heels to better show off their shapely calves (covered by tights rather than trousers) might be a step too far for many 21st Century television viewers. At least the films of the 1940s got the Musketeers' costumes almost right.
We can only hope that the current crop of historical dramas and history-based fantasy series inspire fans to get out there and research what life was really like back then, and then maybe those series will pave the way for more accurate depictions once again in decades to come.