"... any level of comments or insights..."

Whew! Thanks for lowering the bar.

I'm certainly no expert on concrete or decking except that I have lots of each (10 to 30 years old)...

I believe that contractors can add grit or sand to deck surfacing applications in order to improve traction. Boston would be just the place I'd expect contractors to know much about slippery concrete!

You may receive more knowledgeable answers but if not, in your bid process, explore these options with applicants. Some contractors have a one-solution bid for every project so you'd want to avoid them.