You still cannot. However, if you download Libre Office you can do it pretty well in that program. It does not cost anything. I just copied the two versions into their text documents, save them. Leave the "original" open, then under Edit >track changes > compare you open the "edited" one and you can see all the changes.
MacBook Air 13″, macOS 10.15
Optionally, with Xcode installed, FileMerge becomes available for visual text file comparisons. FileMerge is triggered by the following Terminal command with two text files:
opendiff file1.txt file2.txt
and the graphical file comparison appears as:
Installing Xcode just for this feature is a horrible waste of Gigabytes of storage though, unless there are other demanding reasons for its installation.
How to compare documents in Pages