Fortunately the WikiTree Sourcer extension still works on this view for creating citations.
When you use your modified URL, the "Copy Citation" button gives this "United States Census, 1850," database with images, FamilySearch (https://familysearch.org/ark:/61903/3:1:S3HT-64JS-RM2?cc=1401638&wc=95R4-R9P%3A1031308001%2C1031559501%2C1031636201 : 9 April 2016), New Hampshire > Cheshire > Alstead > image 14 of 34; citing NARA microfilm publication M432 (Washington, D.C.: National Archives and Records Administration, n.d.).
You are not the only one. There is a new image viewer, but as you have found, there is a way to get to the old one.
I searched the FamilySearch blog and didn't see it discussed, but it could be there.
It is discussed on the FamilySearch Community. Here is one discussion.
And another discussion.