Unlike Google, Microsoft and Slack, Dropbox does have the top, 5 star, EFF rating for protecting your data from the government... I'm not sure what more they could be doing.
You don't need to use Carousel to be on the receiving end. If the recipent isn't a Carousel user, they receive a link to a nicely formatted gallery page with the option to download all the photos in a zip file or copy them to their Dropbox.
https://www.eff.org/who-has-your-back-government-data-reques...