I probably should not comment (but am,haha) since I've learned that so many jobs have super casual dress codes or even that employess need to wear very casual dress in order to "fit in".
I tend not to like how they look at work, and one reason, I think, is because the average maxi dress is a very thin jersey knit, so tend to look not only casual, but a bit cheap, or revealing the way knit nightwear would be. In addition the average style is cut low in front so even if shoulder straps are covered by a jacket, the combination still might be more beachy than would be in a typical work top. Finally they seem to call for sandals and perhaps more casual sandals. These are just the styles I tend to see most--YMMV.
So to me those types of dresses look less "work-like" than very nice darkwash jeans, footwear, sweater or topper in a smart casual outfit--they don't come across the same way a "work dress" might.
But as in the first sentence, it so depends on your frame of reference--if your colleagues are in shorts, well.....!
Another thing that's been discussed on the forum is more about how you want to present yourself and does the maxidress fit that. For that I don't really put so much stock in "self expression" myself, though I know some do, but to be taken seriously and/or for using dress as part of how you achieve your goals at work, whether that's for corporate-type looks, authority needs, or for having the right "creative" look, or being approachable, or whatever is valuable for functioning in your job. Again coming back around to the idiosyncracies of your own workplace, some folks who "dress up" more than peers or than expected for their function have problems as much as those who dress down.
Wow, I guess just deciding about a maxidress isn't really that huge, but these are the things I think about for wearing a particular style or outfit.