That dress is a typical Kate day visit dress, fussy pattern collar long sleeves ect. She may or may not have taken stuff with her but that dress screams kate at 'work to me' so maybe delivered or brought in lockdown, if she wasn't organised.
I personally prefer a lot of the jumpers/tops she has worn so far...I even quite like the theory Kate is trying to wear the rainbow the symbol for hope after lockdown, that is the kind of literal dressing I can get behind and I like as a pre lockdown normal move from Kate.
This dress is everything Kate gets wrong for me, the collar, the pattern, the fussy sleeves it's all to much have a pattern or a sleeve or one thing but all together is too much her hair wasn't great today either!
However the message they were sending super important and I'm glad mental health especially now is one of the issues William and Kate are still highlighting obviously that's the most important part!