Has Quicken discontinued import addresses (contacts) from CSV files created in Outlook or Excel

While I appreciate Greg's reference, I had already seen the discussion thread he mentioned, as well as several similar threads from previous years/previous versions.  
See, for example:
https://community.quicken.com/discussion/7552527/qwin-2017-h-b-import-address-files

It my experience, over multiple tries over multiple years and versions, that importing contacts into the Quicken Address Book is possible at times, but maddenly impossible at others, even when using the same file, same format, same data. 
Sometimes the data imports fine, other times no data comes in.  

I have experimented with various approaches to try to figure out the "X" factor or factors that produce these inconsistent results.  It does not seem to matter where the file is located; whether the file is a comma separated (CSV) file or a tab delimited (TXT) file; whether the file is created with Excel or Quicken or other programs which can save in CSV or TXT format; or whether you import all the fields in the file, or just some.  It doesn't seem to matter whether you import to a newly created Quicken data file with an empty Address Book, or an existing data file with many entries already in the Address Book.

I will note that it is definitely true that when the import process does work, the new contact entries do show up in the Unassigned group.

I am a fairly sophisticated computer user and have done data manipulation and transfer with a variety of software for many years, but I cannot achieve consistent success importing to the Address Book despite controlling for all of the above variables.  I will note I am using the latest version, latest release of Q HB&R 2019, but I have had similar problems in older Quicken versions.

Even if the import process worked flawlessly every time, I can find little or no specific instructions about the File Import Address Book function in Quicken Help or in online Support, except for a few discussion threads in the Community like Greg referenced.
As I mentioned, Quicken Support agents have variously told me that it is impossible to import into Address Book, or that Quicken doesn't recognize CSV files except for importing security prices.  A

Importing (and exporting) contacts using a standard file format like CSV or tab delimited TXT is a pretty standard feature of most software.  

A new (or even experienced) Quicken user shouldn't have to take a deep dive to find a discussion thread to understand how to use this function, or how to problem solve it when it doesn't work.

If anyone has any suggestions or explanations NOT listed above, I'd love to hear them.  But more importantly, Quicken needs to both figure this out, AND provide clear instruction in the software Help database and train their Support agents how to explain the correct process to users.  Sorry for the extended post.