How create a new Fluid Grid Layout

Do you need this for a course assignment?  If so, tell your instructor that FGLayouts are gone.  Nobody should be using or teaching that method anymore.

If this is for a personal project and you need a responsive layout in a hurry,  go to File > New > Starter Templates > Bootstrap Templates.  Select a layout and hit Create button.

Immediately save and name your document so DW can move the CSS and JS assets from a Temp directory to your local site folder.  One word of caution, DO NOT attempt to edit Bootstrap files.  Use a separate custom stylesheet .

For more on Bootstrap's 12-box grid system for responsive layouts:

Bootstrap 3 Tutorial

As a short term fix, if you need the option to meet a deadline and don't have time to learn the newer and better methods, you can reinstall CC2015 and have that on your machine in parallel to CC2017. As a paid subscriber, you can actually have all 5 CC versions installed on the same machine at the same time under a single subscription. They just won't run at the same time.

Here's how you get old versions back: How to Find and Install Previous Version of Adobe Apps in CC 2015 | Adobe Customer Care Team

The feature has been dropped, as it was difficult to use, and did not work as originally intended.

You could use the Bootstrap feature, but I would recommend learning how to use css flexbox for responsive layouts, as this is, (at the moment) the best solution.

A starter course -

https://www.lynda.com/CSS-tutorials/CSS-Flexbox-First-Look/116352-2.html?utm_source=google&utm_medium=cpc&utm_campaign=l1-US-Search-Web-Flexbox&cid=l1-us:en:ps:lp:prosc:s88:447:all:google:mbm-flexbox_tutorials&utm_content=65287288026&utm_term=%2Bflexbox%20%2Btutorials&src=go-pa&veh=skwd-63931872546_pcrid_65287288026_pkw_%2Bflexbox%20%2Btutorials_pmt_b_pdv_c_ext__plc__trg__agid_10019279346_cmid_176737506_adp_1t1_net_g

Or simply search for flexbox tutorials, but remember not all tutorials are good, (none I have found I would rate as very good)