I have a fully serviced Sony TC-K815S connected to my Strata mk2, and still play the cassette’s dating from the eighties and early nineties. I still buy cassette’s now and then and even made some new mix tapes last year 
In my opinion there are three major problems with cassettes nowadays:
It seams that there aren’t any companies left that are able to make decent to good cassette drive mechanisms anymore (at least not profitable).
Type IV, metal, tapes are not made anymore and the old stock is being sold for ridiculously high prices.
Dolby noise reduction cannot be licensed anymore.