What we define as 'professional' attire is very subjective. Is it unprofessional for a woman to not wear a bra to work if she finds wearing them uncomfortable? I would say currently, it is expected that women wear bras. Men find breasts and cleavage distracting and so in a professional setting the rule is that women cover up. 20 years ago women were expected to wear hosiery, whereas now it is not required to look professional.
Dress codes have naturally evolved and have been very influenced by different industries and fashion small tattoos have a much greater acceptance now than previous generations.
The impact of covid on how we work will see changes: more acceptance of working from home, more virtual meetings etc and dress codes will adapt accordingly.
Rachy - I do love the Queen's 1950's inspired dress code. It has worked for her for many years and makes her instantly identifiable, so much more fun than a black hoodie or polo like the tech industry leaders.